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Filed Pursuant to Rule 497
Registration Statement No. 333-183555

The information in this preliminary prospectus supplement is not complete and may be changed. A registration statement relating to these securities has been filed with and declared effective by the Securities and Exchange Commission. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell and are not soliciting offers to buy these securities in any state where such offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED APRIL 7, 2014

PRELIMINARY PROSPECTUS SUPPLEMENT
(to Prospectus dated August 1, 2013)

            Shares

Main Street Capital Corporation

Common Stock

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         We are offering for sale                shares of our common stock.

         We are a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market ("LMM") companies and debt capital to middle market ("Middle Market") companies. Our LMM companies generally have annual revenues between $10 million and $150 million, and our LMM portfolio investments generally range in size from $5 million to $25 million. Our Middle Market investments are made in businesses that are generally larger in size than our LMM portfolio companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $15 million.

         The LMM and Middle Market securities in which we invest generally would be rated below investment grade if they were rated by rating agencies. Below investment grade securities, which are often referred to as "junk," have predominantly speculative characteristics with respect to the issuer's capacity to pay interest and repay principal. They may also be difficult to value and are illiquid.

         Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company.

         We are an internally managed, closed-end, non-diversified management investment company that has elected to be treated as a business development company under the Investment Company Act of 1940.

         Our common stock is listed on the New York Stock Exchange under the symbol "MAIN." On April     , 2014, the last reported sale price of our common stock on the New York Stock Exchange was $          per share, and the net asset value per share of our common stock on December 31, 2013 (the last date prior to the date of this prospectus supplement on which we determined our net asset value per share) was $19.89.

         Investing in our common stock involves a high degree of risk, and should be considered highly speculative. See "Supplementary Risk Factors" beginning on page S-12 of this prospectus supplement and "Risk Factors" beginning on page 15 of the accompanying prospectus to read about factors you should consider, including the risk of leverage and dilution, before investing in our common stock.

         This prospectus supplement and the accompanying prospectus contain important information about us that a prospective investor should know before investing in our common stock. Please read this prospectus supplement and the accompanying prospectus before investing and keep them for future reference. We file annual, quarterly and current reports, proxy statements and other information with the Securities and Exchange Commission, or SEC. This information is available free of charge by contacting us at 1300 Post Oak Boulevard, Suite 800, Houston, Texas 77056 or by telephone at (713) 350-6000 or on our website at www.mainstcapital.com. Information contained on our website is not incorporated by reference into this prospectus supplement or the accompanying prospectus, and you should not consider that information to be part of this prospectus supplement or the accompanying prospectus. The SEC also maintains a website at www.sec.gov that contains such information.

         The underwriters have the option to purchase up to an additional                shares of common stock at the public offering price, less the underwriting discount, within 30 days from the date of this prospectus supplement. If the option to purchase additional shares is exercised in full, the total public offering price will be $          , the total underwriting discount (3.50%) will be $          , and the total proceeds to us, before deducting estimated expenses payable by us of $200,000, will be $            .

         The Securities and Exchange Commission has not approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

         The underwriters expect to deliver the shares on or about April     , 2014.

   

The date of this prospectus supplement is April     , 2014

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ABOUT THE PROSPECTUS

        This document is in two parts. The first part is this prospectus supplement, which describes the terms of this offering of common stock and also adds to and updates information contained in the accompanying prospectus. The second part is the accompanying prospectus, which provides more information about the common stock we may offer from time to time. To the extent the information contained in this prospectus supplement differs from the information contained in the accompanying prospectus, the information in this prospectus supplement shall control.

        You should rely only on the information contained in this prospectus supplement and the accompanying prospectus. Neither we nor the underwriters have authorized any other person to provide you with different information from that contained in this prospectus supplement or the accompanying prospectus. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus supplement and the accompanying prospectus do not constitute an offer to sell, or a solicitation of an offer to buy, any shares of our common stock by any person in any jurisdiction where it is unlawful for that person to make such an offer or solicitation or to any person in any jurisdiction to whom it is unlawful to make such an offer or solicitation. The information contained in this prospectus supplement and the accompanying prospectus is complete and accurate only as of their respective dates, regardless of the time of their delivery or sale of our common stock. This prospectus supplement supersedes the accompanying prospectus to the extent it contains information different from or additional to the information in that prospectus.

Forward-Looking Statements

        Information contained in this prospectus supplement and the accompanying prospectus may contain forward-looking statements, which can be identified by the use of forward-looking terminology such as "may," "will," "expect," "intend," "anticipate," "estimate," or "continue" or the negative thereof or other variations thereon or comparable terminology. The matters described in the sections titled "Supplementary Risk Factors" in this prospectus supplement and "Risk Factors" in the accompanying prospectus and certain other factors noted throughout this prospectus supplement and the accompanying prospectus constitute cautionary statements identifying important factors with respect to any such forward-looking statements, including certain risks and uncertainties that could cause actual results to differ materially from those in such forward-looking statements. We undertake no obligation to revise or update any forward-looking statements but advise you to consult any additional disclosures that we may make directly to you or through reports that we may file in the future with the SEC, including annual reports on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K. We note that the safe harbor for forward-looking statements provided by the Private Securities Litigation Reform Act of 1995 does not apply to statements made in this prospectus supplement or the accompanying prospectus.

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SUPPLEMENTARY RISK FACTORS

        Investing in our securities involves a number of significant risks. In addition to the other information contained in this prospectus supplement and the accompanying prospectus, you should consider carefully the following supplementary risk factors together with the risk factors beginning on page 15 of the accompanying prospectus before making an investment in our securities. The risks set out below and in the accompanying prospectus are not the only risks we face. Additional risks and uncertainties not presently known to us or not presently deemed material by us might also impair our operations and performance. If any of the events described herein or in the accompanying prospectus occur, our business, financial condition and results of operations could be materially and adversely affected. In such case, our net asset value and the trading price of our common stock could decline, and you may lose all or part of your investment.

Risks Relating to Our Business and Structure

We are dependent upon our key investment personnel for our future success.

        We depend on the members of our investment team, particularly Vincent D. Foster, Dwayne L. Hyzak, Curtis L. Hartman, David L. Magdol, Travis L. Haley, Nicholas T. Meserve, Robert M. Shuford, and Rodger A. Stout for the identification, review, final selection, structuring, closing and monitoring of our investments. These employees have significant investment expertise and relationships that we rely on to implement our business plan. Although we have entered into a non- compete agreement with Mr. Foster, we have no guarantee that he or any other employees will remain employed with us. If we lose the services of these individuals, we may not be able to operate our business as we expect, and our ability to compete could be harmed, which could cause our operating results to suffer.

There are significant potential conflicts of interest which could impact our investment returns.

        Our executive officers and employees, through the External Investment Manager, may manage other investment funds that operate in the same or a related line of business as we do. Accordingly, they may have obligations to such other entities, the fulfillment of which obligations may not be in the best interests of us or our stockholders. During May 2012, MSCC entered into an investment sub-advisory agreement with HMS Adviser, LP ("HMS Adviser"), which is the investment advisor to HMS Income Fund, Inc. ("HMS Income"), a non publicly-traded BDC whose registration statement on Form N-2 was declared effective by the SEC in June 2012, to provide certain investment advisory services to HMS Adviser. In December 2013, after obtaining required relief from the SEC, MSCC assigned the sub-advisory agreement to the External Investment Manager since the fees received from such arrangement could otherwise have negative consequences on MSCC's ability to meet the source-of-income requirement necessary for it to maintain its RIC tax treatment. Under the investment sub-advisory agreement, the External Investment Manager is entitled to 50% of the base management fee and the incentive fees earned by HMS Adviser under its advisory agreement with HMS Income. However, MSCC and the External Investment Manager agreed to waive all such fees from the effective date of HMS Adviser's registration statement on Form N-2 through December 31, 2013. As a result, as of December 31, 2013, neither MSCC nor the External Investment Manager had received any base management fee or incentive fees under the investment sub-advisory agreement and neither is due any unpaid compensation for any base management fee or incentive fees under the investment sub-advisory agreement. Neither MSCC nor the External Investment Manager has waived the External Investment Manager's management or incentive fees after December 31, 2013 and, as a result, the External Investment Manager began accruing such fees on January 1, 2014. The sub-advisory relationship requires us to commit resources to achieving HMS Income's investment objective, while such resources were previously solely devoted to achieving our investment objective. Our investment objective and investment strategies are very similar to those of HMS Income and it is likely that an investment appropriate for us or HMS Income would be appropriate for the other entity. As a result, we and HMS

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Income have requested an exemptive order from the SEC permitting co-investments by us and HMS Income in certain negotiated investments where our co-investing would otherwise be prohibited under the 1940 Act. Upon the receipt of the order, we intend to make such co-investments with HMS Income in accordance with the conditions of the order. The order requires, among other things, that we and the External Investment Manager consider whether each such investment opportunity is appropriate for HMS Income and, if it is appropriate, to propose an allocation of the investment opportunity between us and HMS Income. As a consequence, it may be more difficult for us to maintain or increase the size of our investment portfolio in the future. Although we will endeavor to allocate investment opportunities in a fair and equitable manner, including in accordance with the conditions set forth in any exemptive order issued by the SEC when relying on such order, we may face conflicts in allocating investment opportunities between us and HMS Income. We have implemented an allocation policy to ensure the equitable distribution of investment opportunities and, as a result, may be unable to participate in certain investments prior to receiving such relief.

Because we borrow money, the potential for gain or loss on amounts invested in us is magnified and may increase the risk of investing in us.

        Borrowings, also known as leverage, magnify the potential for loss on investments in our indebtedness and gain or loss on investments in our equity capital. As we use leverage to partially finance our investments, you will experience increased risks of investing in our securities. We, through the Funds, issue debt securities guaranteed by the SBA and sold in the capital markets. As a result of its guarantee of the debt securities, the SBA has fixed dollar claims on the assets of the Funds that are superior to the claims of our securities holders. We may also borrow from banks and other lenders, including under our Credit Facility, and may issue debt securities or enter into other types of borrowing arrangements in the future. See "Management's Discussion and Analysis of Financial Condition and Results of Operations—Capital Resources" in this prospectus supplement for a discussion regarding our outstanding indebtedness. If the value of our assets increases, then leveraging would cause the net asset value attributable to our common stock to increase more sharply than it would have had we not leveraged. Conversely, if the value of our assets decreases, leveraging would cause net asset value to decline more sharply than it otherwise would have had we not leveraged our business. Similarly, any increase in our income in excess of interest payable on the borrowed funds would cause our net investment income to increase more than it would without the leverage, while any decrease in our income would cause net investment income to decline more sharply than it would have had we not borrowed. Such a decline could negatively affect our ability to pay common stock dividends, scheduled debt payments or other payments related to our securities. Leverage is generally considered a speculative investment technique.

        As of December 31, 2013, we, through the Funds, had $200.2 million of outstanding indebtedness guaranteed by the SBA, which had a weighted average annualized interest cost of approximately 3.8% (exclusive of deferred financing costs). The debentures guaranteed by the SBA have a maturity of ten years, with a current weighted average remaining maturity of 7.3 years as of December 31, 2013, and require semi-annual payments of interest. We will need to generate sufficient cash flow to make required interest payments on the debentures. If we are unable to meet the financial obligations under the debentures, the SBA, as a creditor, will have a superior claim to the assets of the Funds over our stockholders in the event we liquidate or the SBA exercises its remedies under such debentures as the result of a default by us.

        In addition, as of December 31, 2013, we had $237.0 million outstanding under our Credit Facility. Borrowings under the Credit Facility bear interest, subject to our election, on a per annum basis equal to (i) the applicable LIBOR rate (0.17% as of December 31, 2013) plus 2.25% or (ii) the applicable base rate (Prime Rate, 3.25% as of December 31, 2013) plus 1.25%. Main Street pays unused commitment fees of 0.25% per annum on the average unused lender commitments under the Credit

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Facility. If we are unable to meet the financial obligations under the Credit Facility, the Credit Facility lending group will have a superior claim to the assets of MSCC and its subsidiaries (excluding the assets of the Funds) over our stockholders in the event we liquidate or the lending group exercises its remedies under the Credit Facility as the result of a default by us.

        In April 2013, we issued $92.0 million in aggregate principal amount of 6.125% Notes due 2023 (the "Notes"). As of December 31, 2013, the outstanding balance of the Notes was $90.9 million. The Notes are unsecured obligations and rank pari passu with our current and future senior unsecured indebtedness; senior to any of our future indebtedness that expressly provides it is subordinated to the Notes; effectively subordinated to all of our existing and future secured indebtedness, to the extent of the value of the assets securing such indebtedness, including borrowings under our Credit Facility; and structurally subordinated to all existing and future indebtedness and other obligations of any of our subsidiaries, including without limitation, the indebtedness of the Funds. The Notes mature on April 1, 2023, and may be redeemed in whole or in part at any time or from time to time at Main Street's option on or after April 1, 2018. The Notes bear interest at a rate of 6.125%.

        Illustration.    The following table illustrates the effect of leverage on returns from an investment in our common stock assuming various annual returns, net of expenses. The calculations in the table below are hypothetical and actual returns may be higher or lower than those appearing below.

Assumed Return on Our Portfolio(1)
(net of expenses)

        Our ability to achieve our investment objective may depend in part on our ability to access additional leverage on favorable terms by issuing debentures guaranteed by the SBA through the Funds, by borrowing from banks or insurance companies or by issuing other debt securities and there can be no assurance that such additional leverage can in fact be achieved.

Further downgrades of the U.S. credit rating, automatic spending cuts or another government shutdown could negatively impact our liquidity, financial condition and earnings.

        Recent U.S. debt ceiling and budget deficit concerns have increased the possibility of additional credit-rating downgrades and economic slowdowns, or a recession in the U.S. Although U.S. lawmakers passed legislation to raise the federal debt ceiling on multiple occasions, ratings agencies have lowered or threatened to lower the long-term sovereign credit rating on the United States. The impact of this or any further downgrades to the U.S. government's sovereign credit rating or its perceived creditworthiness could adversely affect the U.S. and global financial markets and economic conditions. Absent further quantitative easing by the Federal Reserve, these developments could cause interest rates and borrowing costs to rise, which may negatively impact our ability to access the debt markets on favorable terms. In addition, disagreement over the federal budget has caused the U.S. federal government to shut down for periods of time. Continued adverse political and economic conditions could have a material adverse effect on our business, financial condition and results of operations.

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It is unclear how increased regulatory oversight and changes in the method for determining LIBOR may affect the value of the financial obligations to be held or issued by us that are linked to LIBOR, or how such changes could affect our results of operations or financial condition.

        As a result of concerns about the accuracy of the calculation of LIBOR, a number of British Bankers' Association, or BBA, member banks entered into settlements with certain regulators and law enforcement agencies with respect to the alleged manipulation of LIBOR, and there are ongoing investigations by regulators and governmental authorities in various jurisdictions. Following a review of LIBOR conducted at the request of the U.K. government, on September 28, 2012, recommendations for reforming the setting and governing of LIBOR were released, which are referred to as the Wheatley Review. The Wheatley Review made a number of recommendations for changes with respect to LIBOR, including the introduction of S-5 statutory regulation of LIBOR, the transfer of responsibility for LIBOR from the BBA to an independent administrator, changes to the method of the compilation of lending rates and new regulatory oversight and enforcement mechanisms for rate-setting and a reduction in the number of currencies and tenors for which LIBOR is published. Based on the Wheatley Review and on a subsequent public and governmental consultation process, on March 25, 2013, the U.K. Financial Services Authority published final rules for the U.K. Financial Conduct Authority's regulation and supervision of LIBOR, which are referred to as the FCA Rules. In particular, the FCA Rules include requirements that (1) an independent LIBOR administrator monitor and survey LIBOR submissions to identify breaches of practice standards and/or potentially manipulative behavior, and (2) firms submitting data to LIBOR establish and maintain a clear conflicts of interest policy and appropriate systems and controls. The FCA Rules took effect on April 2, 2013, and on July 9, 2013, NYSE Euronext was chosen to serve as the independent LIBOR administrator commencing in 2014. It is uncertain what additional regulatory changes or what changes, if any, in the method of determining LIBOR may be required or made by the U.K. government or other governmental or regulatory authorities. Accordingly, uncertainty as to the nature of such changes may adversely affect the market for or value of any LIBOR-linked securities, loans, derivatives and other financial obligations or extensions of credit held by or due to us or on our overall financial condition or results of operations. In addition, any further changes or reforms to the determination or supervision of LIBOR may result in a sudden or prolonged increase or decrease in reported LIBOR, which could have an adverse impact on the market for or value of any LIBOR-linked securities, loans, derivatives and other financial obligations or extensions of credit held by or due to us or on our overall financial condition or results of operations.

We are highly dependent on information systems and systems failures could significantly disrupt our business, which may, in turn, negatively affect the market price of our common stock and our ability to pay dividends.

        Our business is highly dependent on our and third parties' communications and information systems. Any failure or interruption of those systems, including as a result of the termination of an agreement with any third-party service providers, could cause delays or other problems in our activities. Our financial, accounting, data processing, backup or other operating systems and facilities may fail to operate properly or become disabled or damaged as a result of a number of factors including events that are wholly or partially beyond our control and adversely affect our business. There could be:

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sudden electrical or telecommunications outages;



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natural disasters such as earthquakes, tornadoes and hurricanes;



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disease pandemics;



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events arising from local or larger scale political or social matters, including terrorist acts; and



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cyber attacks.

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These events, in turn, could have a material adverse effect on our operating results and negatively affect the market price of our common stock and our ability to pay dividends to our stockholders.

Risks Relating to Our Securities

The market price of our securities may be volatile and fluctuate significantly.

        Fluctuations in the trading prices of our securities may adversely affect the liquidity of the trading market for our securities and, if we seek to raise capital through future securities offerings, our ability to raise such capital. The market price and liquidity of the market for our securities may be significantly affected by numerous factors, some of which are beyond our control and may not be directly related to our operating performance. These factors include:

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significant volatility in the market price and trading volume of securities of BDCs or other companies in our sector, which are not necessarily related to the operating performance of these companies;



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changes in regulatory policies, accounting pronouncements or tax guidelines, particularly with respect to RICs, BDCs or SBICs;



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the exclusion of our common stock from certain market indices, such as the Russell 2000 Financial Services Index, could reduce the ability of certain investment funds to own our common stock and put short term selling pressure on our common stock;



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inability to obtain any exemptive relief that may be required by us in the future from the SEC;



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loss of our BDC or RIC status or either of the Funds' status as an SBIC;



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changes in our earnings or variations in our operating results;



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changes in the value of our portfolio of investments;



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any shortfall in our investment income or net investment income or any increase in losses from levels expected by investors or securities analysts;



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loss of a major funding source;



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fluctuations in interest rates;



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the operating performance of companies comparable to us;



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departure of our key personnel;



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global or national credit market changes; and



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general economic trends and other external factors.

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USE OF PROCEEDS

        The net proceeds from the sale of the                shares of common stock in this offering are $        , and $         if the underwriter's option to purchase additional shares is exercised in full, after deducting the underwriting discount and estimated offering expenses payable by us.

        We intend to initially use the net proceeds from this offering to repay outstanding debt borrowed under our $445.0 million Credit Facility. However, through re-borrowing of the initial repayments under our $445.0 million Credit Facility, we intend to use the net proceeds from this offering to make investments in accordance with our investment objective and strategies described in this prospectus supplement and the accompanying prospectus, to make investments in marketable securities and idle funds investments, which may include investments in secured intermediate term bank debt, rated debt securities and other income producing investments, to pay our operating expenses and other cash obligations, and for general corporate purposes. Our ability to achieve our investment objective may be limited to the extent that the net proceeds from an offering, pending full investment, are held in interest bearing deposits or other short-term instruments. See "Risk Factors—Risks Relating to Our Securities—We may be unable to invest a significant portion of the net proceeds from an offering or from exiting an investment or other capital on acceptable terms, which could harm our financial condition and operating results" in the accompanying prospectus.

        At April 4, 2014, we had approximately $227.0 million outstanding under our $445.0 million Credit Facility. Our Credit Facility matures in September 2018, unless extended, and bears interest, at our election, on a per annum basis equal to (i) the applicable LIBOR rate plus 2.25% or (ii) the applicable base rate plus 1.25%. Amounts repaid under our $445.0 million Credit Facility will remain available for future borrowings. As of December 31, 2013, the interest rate on our $445.0 million Credit Facility was 2.4%.

        Affiliates of Raymond James & Associates, Inc., Goldman, Sachs & Co. and RBC Capital Markets, LLC, underwriters in this offering, act as lenders and/or agents under our $445.0 million Credit Facility. As described above, we intend to use net proceeds of this offering to repay the outstanding indebtedness under this Credit Facility, and such affiliates therefore may receive a portion of the proceeds from this offering through the repayment of those borrowings. See "Underwriting—Conflicts of Interest" below.

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CAPITALIZATION

        The following table sets forth our capitalization:

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on an actual basis as of December 31, 2013; and



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on an as-adjusted basis giving effect to the sale of            shares of our common stock in this offering at the public offering price of $            per share, less estimated underwriting discounts and offering expenses payable by us.

        This table should be read in conjunction with "Management's Discussion and Analysis of Financial Condition and Results of Operations" and "Audited Financial Statements" in this prospectus supplement.

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PRICE RANGE OF COMMON STOCK AND DISTRIBUTIONS

        Our common stock is traded on the New York Stock Exchange ("NYSE") under the symbol "MAIN." Prior to October 14, 2010, our common stock was traded on the NASDAQ Global Select Market under the same symbol "MAIN." Our common stock began trading on the NASDAQ Global Select Market on October 5, 2007. Prior to that date, there was no established public trading market for our common stock.

        The following table sets forth, for each fiscal quarter during 2014, 2013 and 2012, the range of high and low closing prices of our common stock as reported on the NYSE, and the sales price as a percentage of the net asset value per share of our common stock.

        On April 4, 2014 the last sale price of our common stock on the NYSE was $33.18 per share, and there were approximately 193 holders of record of the common stock which did not include stockholders for whom shares are held in "nominee" or "street name." The net asset value per share of our common stock on December 31, 2013 (the last date prior to the date of this prospectus supplement on which we determined our net asset value per share) was $19.89, and the April 4, 2014 closing price of our common stock was 167% of this net asset value per share.

        Shares of BDCs may trade at a market price that is less than the value of the net assets attributable to those shares. The possibility that our shares of common stock will trade at a discount from net asset value per share or at premiums that are unsustainable over the long term are separate and distinct from the risk that our net asset value per share will decrease. It is not possible to predict whether our common stock will trade at, above, or below net asset value per share. Since our IPO in October 2007, our shares of common stock have traded at prices both less than and exceeding our net asset value per share.

        We currently pay monthly dividends to our stockholders. Our monthly dividends, if any, will be determined by our Board of Directors on a quarterly basis. In addition to our monthly dividends, in January 2013 we began paying periodic supplemental dividends out of our undistributed taxable income, or spillover income. Our future supplemental dividends, if any, will be determined by our Board of Directors on a periodic basis.

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        The following table summarizes our dividends declared to date:

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        To obtain and maintain RIC tax treatment, we must, among other things, distribute at least 90% of our net ordinary income and realized net short- term capital gains in excess of realized net long-term capital losses, if any. We will be subject to a 4% nondeductible federal excise tax on certain undistributed taxable income unless we distribute in a timely manner an amount at least equal to the sum of (1) 98% of our net ordinary income for each calendar year, (2) 98.2% of our capital gain net income for the one-year period ending December 31 in that calendar year and (3) any income recognized, but not distributed, in preceding years (the "Excise Tax Avoidance Requirement"). Dividends declared and paid by us in a year will generally differ from taxable income for that year, as such dividends may include the distribution of current year taxable income, less amounts carried over into the following year, and the distribution of prior year taxable income carried over into and distributed in the current year. For amounts we carry over into the following year, we will be required to pay a 4% excise tax on the amount by which 98% of our annual ordinary taxable income and 98.2% of capital gains exceeds our distributions for the year. We may retain for investment some or all of our net capital gains (i.e., realized net long-term capital gains in excess of realized net short-term capital losses) and treat such amounts as deemed distributions to our stockholders. If we do this, our stockholders will be treated as if they had received actual distributions of the capital gains we retained and then reinvested the net after-tax proceeds in our common stock. In general, our stockholders also would be eligible to claim a tax credit (or, in certain circumstances, a tax refund) equal to their allocable shares of the tax we paid on the capital gains deemed distributed to them. We can offer no assurance that we will achieve results that will permit the payment of any cash distributions and, if we issue senior securities, we may be prohibited from making distributions if doing so causes us to fail to maintain the asset coverage ratios stipulated by the 1940 Act or if distributions are limited by the terms of any of our borrowings.

        We may distribute taxable dividends that are payable in part in our stock. Under certain applicable provisions of the Code and the Treasury regulations, distributions payable by us in cash or in shares of stock (at the stockholders election) would satisfy the Annual Distribution Requirement. The IRS has issued private letter rulings providing that a dividend payable in stock or in cash at the election of the stockholders will be treated as a taxable dividend eligible for the dividends paid deduction provided that at least 20% of the total dividend is payable in cash and certain other requirements are satisfied. Taxable stockholders receiving such dividends will be required to include the full amount of the dividend as ordinary income (or as long-term capital gain to the extent such dividend is properly

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reported as a capital gain dividend), to the extent of our current and accumulated earnings and profits for United States federal income tax purposes. As a result, a U.S. stockholder may be required to pay tax with respect to such dividends in excess of any cash received. If a U.S. stockholder sells the stock it receives as a dividend in order to pay this tax, the sales proceeds may be less than the amount included in income with respect to the dividend, depending on the market price of our stock at the time of the sale. Furthermore, with respect to non-U.S. stockholders, we may be required to withhold U.S. tax with respect to such dividends, including in respect of all or a portion of such dividend that is payable in stock. In addition, if a significant number of our stockholders determine to sell shares of our stock in order to pay taxes owed on dividends, it may put downward pressure on the trading price of our stock.

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SELECTED FINANCIAL DATA

        The selected financial and other data as of and for the years ended December 31, 2013, 2012, 2011, 2010 and 2009 have been derived from consolidated financial statements that have been audited by Grant Thornton LLP, an independent registered public accounting firm. You should read this selected financial and other data in conjunction with our "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the financial statements and related notes thereto in the accompanying prospectus and "Management's Discussion and Analysis of Financial Condition and Results of Operations," "Senior Securities" and "Audited Financial Statements" in this prospectus supplement.

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MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS

        The following discussion should be read in conjunction with our consolidated financial statements and notes thereto contained elsewhere in this prospectus supplement.

        Statements we make in the following discussion which express a belief, expectation or intention, as well as those that are not historical fact, are forward-looking statements that are subject to risks, uncertainties and assumptions. Our actual results, performance or achievements, or industry results, could differ materially from those we express in the following discussion as a result of a variety of factors, including the risks and uncertainties we have referred to under the headings "Forward-Looking Statements" and "Supplementary Risk Factors" in this prospectus supplement and "Cautionary Statement Concerning Forward-Looking Statements" and "Risk Factors" in the accompanying prospectus.

ORGANIZATION

        Main Street Capital Corporation ("MSCC") was formed in March 2007 for the purpose of (i) acquiring 100% of the equity interests of Main Street Mezzanine Fund, LP ("MSMF") and its general partner, Main Street Mezzanine Management, LLC ("MSMF GP"), (ii) acquiring 100% of the equity interests of Main Street Capital Partners, LLC (the "Internal Investment Manager"), (iii) raising capital in an initial public offering, which was completed in October 2007 (the "IPO"), and (iv) thereafter operating as an internally managed business development company ("BDC") under the Investment Company Act of 1940, as amended (the "1940 Act"). MSMF is licensed as a Small Business Investment Company ("SBIC") by the United States Small Business Administration ("SBA") and the Internal Investment Manager acts as MSMF's manager and investment adviser. Because the Internal Investment Manager, which employs all of the executive officers and other employees of MSCC, is wholly owned by us, we do not pay any external investment advisory fees, but instead we incur the operating costs associated with employing investment and portfolio management professionals through the Internal Investment Manager. The IPO and related transactions discussed above were consummated in October 2007 and are collectively termed the "Formation Transactions."

        During January 2010, MSCC acquired (the "Exchange Offer") approximately 88% of the total dollar value of the limited partner interests in Main Street Capital II, LP ("MSC II" and, together with MSMF, the "Funds") and 100% of the membership interests in the general partner of MSC II, Main Street Capital II GP, LLC ("MSC II GP"). MSC II is an investment fund that operates as an SBIC and commenced operations in January 2006. During the first quarter of 2012, MSCC acquired all of the remaining minority ownership in the total dollar value of the MSC II limited partnership interests (the "Final MSC II Exchange"). The Exchange Offer and related transactions, including the acquisition of MSC II GP interests and the Final MSC II Exchange, are collectively termed the "Exchange Offer Transactions."

        MSC Adviser I, LLC (the "External Investment Manager" and, together with the Internal Investment Manager, the "Investment Managers") was formed in November 2013 as a wholly owned subsidiary of MSCC to provide investment management advisory and other services to parties other than MSCC and its subsidiaries ("External Parties") and to receive fee income for such services. MSCC has been granted no-action relief by the Securities and Exchange Commission to allow the External Investment Manager to register as a registered investment adviser ("RIA") under Investment Advisers Act of 1940, as amended (the "Advisers Act"), to provide investment management services to External Parties. The External Investment Manager is accounted for as a portfolio investment of MSCC, since the External Investment Manager conducts all of its investment management activities for parties outside of MSCC and its consolidated subsidiaries.

        MSCC has elected to be treated for federal income tax purposes as a regulated investment company ("RIC") under Subchapter M of the Internal Revenue Code of 1986, as amended (the

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"Code"). As a result, MSCC generally will not pay corporate-level federal income taxes on any net ordinary income or capital gains that it distributes to its stockholders as dividends.

        MSCC has direct and indirect wholly owned subsidiaries that have elected to be taxable entities (the "Taxable Subsidiaries"). The primary purpose of these entities is to hold certain investments that generate "pass through" income for tax purposes. The Investment Managers are both also direct wholly owned subsidiaries that have elected to be taxable entities. The Taxable Subsidiaries and the Investment Managers are each taxed at their normal corporate tax rates based on their taxable income.

        Unless otherwise noted or the context otherwise indicates, the terms "we," "us," "our" and "Main Street" refer to MSCC and its consolidated subsidiaries, which include the Funds, the Taxable Subsidiaries and, beginning April 1, 2013, the Internal Investment Manager.

OVERVIEW

        We are a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market ("LMM") companies and debt capital to middle market ("Middle Market") companies. Our portfolio investments are typically made to support management buyouts, recapitalizations, growth financings, refinancings and acquisitions of companies that operate in diverse industry sectors. We seek to partner with entrepreneurs, business owners and management teams and generally provide "one stop" financing alternatives within our LMM portfolio. We invest primarily in secured debt investments, equity investments, warrants and other securities of LMM companies based in the United States and in secured debt investments of Middle Market companies generally headquartered in the United States. Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. Our LMM companies generally have annual revenues between $10 million and $150 million, and our LMM portfolio investments generally range in size from $5 million to $25 million. Our Middle Market investments are made in businesses that are generally larger in size than our LMM portfolio companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $15 million. Our private loan ("Private Loan") investments are made in businesses that are consistent with the size of companies in our LMM portfolio or our Middle Market portfolio, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. The structure, terms and conditions for these Private Loan investments are typically consistent with the structure, terms and conditions for the loans made in our LMM portfolio or Middle Market portfolio.

        Our other portfolio ("Other Portfolio") investments primarily consist of investments which are not consistent with the typical profiles for our LMM, Middle Market or Private Loan portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

        Our external asset management business is conducted through our External Investment Manager. We have entered into an agreement through the Internal Investment Manager to provide the External Investment Manager with asset management service support for HMS Income Fund, Inc. ("HMS Income"). Through this agreement, we provide management and other services to the External Investment Manager, as well as access to our employees, infrastructure, business relationships, management expertise and capital raising capabilities. Beginning in the first quarter of 2014, we charge the External Investment Manager a fee for the use of these services. The External Investment Manager earns management fees based on the assets of the funds under management and may earn incentive fees, or a carried interest, based on the performance of the funds managed.

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        We seek to fill the current financing gap for LMM businesses, which, historically, have had more limited access to financing from commercial banks and other traditional sources. The underserved nature of the LMM creates the opportunity for us to meet the financing needs of LMM companies while also negotiating favorable transaction terms and equity participations. Our ability to invest across a company's capital structure, from senior secured loans to equity securities, allows us to offer portfolio companies a comprehensive suite of financing options, or a "one stop" financing solution. Providing customized, "one stop" financing solutions has become even more relevant to our LMM portfolio companies in the current investing environment. We generally seek to partner directly with entrepreneurs, management teams and business owners in making our investments. Our LMM portfolio debt investments are generally secured by a first lien on the assets of the portfolio company and typically have a term of between five and seven years. We believe that our LMM investment strategy has a lower correlation to the broader debt and equity markets.

        As of December 31, 2013, we had debt and equity investments in 62 LMM portfolio companies with an aggregate fair value of approximately $659.4 million, with a total cost basis of approximately $543.3 million and a weighted average annual effective yield on our LMM debt investments of approximately 14.7%. As of December 31, 2013, approximately 76% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 86% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At December 31, 2013, we had equity ownership in approximately 94% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 33%. As of December 31, 2012, we had debt and equity investments in 56 LMM portfolio companies with an aggregate fair value of approximately $482.9 million, with a total cost basis of approximately $380.5 million, and a weighted average annual effective yield on our LMM debt investments of approximately 14.3%. As of December 31, 2012, approximately 75% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 93% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At December 31, 2012, we had equity ownership in approximately 93% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 33%. The weighted average annual yields were computed using the effective interest rates for all debt investments at December 31, 2013 and 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments and any debt investments on non-accrual status.

        In addition to our LMM investment strategy, we pursue investments in Middle Market companies. Our Middle Market portfolio investments primarily consist of direct investments in or secondary purchases of interest-bearing debt securities in privately held companies that are generally larger in size than the LMM companies included in our LMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien on the assets of the company and typically have an expected duration of between three and five years.

        As of December 31, 2013, we had Middle Market portfolio investments in 92 companies collectively totaling approximately $471.5 million in fair value with a total cost basis of approximately $468.3 million. The weighted average EBITDA for the 92 Middle Market portfolio company investments was approximately $79.0 million as of December 31, 2013. As of December 31, 2013, substantially all of our Middle Market portfolio investments were in the form of debt investments and approximately 92% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Middle Market portfolio debt investments was approximately 7.8% as of December 31, 2013. As of December 31, 2012, we had Middle Market portfolio investments in 79 companies, collectively totaling approximately $352.0 million in fair value with a total cost basis of approximately $348.1 million. The weighted average EBITDA for the 79 Middle Market portfolio company investments was approximately $93.5 million as of

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December 31, 2012. As of December 31, 2012, substantially all of our Middle Market portfolio investments were in the form of debt investments and approximately 91% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Middle Market portfolio debt investments was approximately 8.0% as of December 31, 2012. The weighted average annual yields were computed using the effective interest rates for all debt investments at December 31, 2013 and 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments.

        Our Private Loan portfolio investments primarily consist of investments in interest-bearing debt securities in companies that are consistent with the size of the companies included in our LMM portfolio or our Middle Market portfolio. Our Private Loan portfolio debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have a term of between three and seven years.

        As of December 31, 2013, we had Private Loan portfolio investments in 15 companies, collectively totaling approximately $111.5 million in fair value with a total cost basis of approximately $111.3 million. The weighted average EBITDA for the 15 Private Loan portfolio company investments was approximately $18.4 million as of December 31, 2013. As of December 31, 2013, 95% of our Private Loan portfolio investments were in the form of debt investments and 98% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Private Loan portfolio debt investments was approximately 11.3% as of December 31, 2013. As of December 31, 2012, we had Private Loan portfolio investments in 9 companies, collectively totaling approximately $65.5 million in fair value with a total cost basis of approximately $64.9 million. The weighted average EBITDA for the 9 Private Loan portfolio company investments was approximately $45.6 million as of December 31, 2012. As of December 31, 2012, approximately 99% of our Private Loan portfolio investments were in the form of debt investments and all such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Private Loan portfolio debt investments was approximately 14.8% as of December 31, 2012. The weighted average annual yields were computed using the effective interest rates for all debt investments at December 31, 2013 and 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments.

        As of December 31, 2013, we had Other Portfolio investments in six companies collectively totaling approximately $42.8 million in fair value and approximately $40.1 million in cost basis and which comprised 3.3% of our Investment Portfolio at fair value as of December 31, 2013. As of December 31, 2012, we had Other Portfolio investments in three companies, collectively totaling approximately $24.1 million in fair value and approximately $23.6 million in cost basis and which comprised 2.6% of our Investment Portfolio at fair value as of December 31, 2012.

        As discussed further above, we hold an investment in the External Investment Manager, a wholly owned subsidiary that is treated as a portfolio investment. As of December 31, 2013, we had no cost basis in this investment and the investment had a fair value of $1.1 million, which comprised 0.1% of our Investment Portfolio.

        During 2013, we began categorizing certain of our portfolio investments that were previously categorized as LMM portfolio investments or Middle Market portfolio investments as Private Loan portfolio investments to provide a separate classification based upon the nature in which such investments are originated. During the year ended December 31, 2013, there were ten portfolio company investment transfers from the LMM and Middle Market portfolio investment categories to the Private Loan portfolio investment category totaling $69.6 million in fair value and $69.0 million in cost on the date of transfer.

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        Our portfolio investments are generally made through MSCC and the Funds. MSCC and the Funds share the same investment strategies and criteria, although they are subject to different regulatory regimes. An investor's return in MSCC will depend, in part, on the Funds' investment returns as MSMF and MSC II are both wholly owned subsidiaries of MSCC.

        The level of new portfolio investment activity will fluctuate from period to period based upon our view of the current economic fundamentals, our ability to identify new investment opportunities that meet our investment criteria, and our ability to consummate the identified opportunities. The level of new investment activity, and associated interest and fee income, will directly impact future investment income. In addition, the level of dividends paid by portfolio companies and the portion of our portfolio debt investments on non-accrual status will directly impact future investment income. While we intend to grow our portfolio and our investment income over the long-term, our growth and our operating results may be more limited during depressed economic periods. However, we intend to appropriately manage our cost structure and liquidity position based on applicable economic conditions and our investment outlook. The level of realized gains or losses and unrealized appreciation or depreciation will also fluctuate depending upon portfolio activity, economic conditions and the performance of our individual portfolio companies. The changes in realized gains and losses and unrealized appreciation or depreciation could have a material impact on our operating results.

        MSCC and its consolidated subsidiaries are internally managed by the Internal Investment Manager, a wholly owned subsidiary of MSCC, which employs all of the executive officers and other employees of Main Street. Because the Internal Investment Manager is wholly owned by MSCC, Main Street does not pay any external investment advisory fees, but instead incurs the operating costs associated with employing investment and portfolio management professionals through the Internal Investment Manager. We believe that our internally managed structure provides us with a beneficial operating expense structure when compared to other publicly-traded and privately-held investment firms which are externally managed, and our internally managed structure allows us the opportunity to leverage our non-interest operating expenses as we grow our investment portfolio. For the year ended December 31, 2013, the ratio of our total operating expenses, excluding interest expense and excluding the effect of the accelerated vesting of restricted stock (as discussed further below in "Discussion and Analysis of Results of Operations—Comparison of the years ended December 31, 2013 and 2012"), as a percentage of our quarterly average total assets was 1.7% compared to 1.8% for the year ended December 31, 2012. Including the effect of the accelerated vesting of restricted stock, the ratio for the year ended 2013 would have been 1.8%.

        During May 2012, MSCC entered into an investment sub-advisory agreement with HMS Adviser, LP ("HMS Adviser"), which is the investment advisor to HMS Income Fund, Inc. ("HMS Income"), a non publicly-traded BDC whose registration statement on Form N-2 was declared effective by the SEC in June 2012, to provide certain investment advisory services to HMS Adviser. In December 2013, after obtaining required relief from the SEC, MSCC assigned the sub-advisory agreement to the External Investment Manager since the fees received from such arrangement could otherwise have negative consequences on MSCC's ability to meet the source-of-income requirement necessary for it to maintain its RIC tax treatment. Under the investment sub-advisory agreement, the External Investment Manager is entitled to 50% of the base management fee and the incentive fees earned by HMS Adviser under its advisory agreement with HMS Income. However, MSCC and the External Investment Manager agreed to waive all such fees from the effective date of HMS Adviser's registration statement on Form N-2 through December 31, 2013. As a result, as of December 31, 2013, neither MSCC nor the External Investment Manager had received any base management fee or incentive fees under the investment sub-advisory agreement and neither is due any unpaid compensation for any base management fee or incentive fees under the investment sub-advisory agreement. Neither MSCC nor the External Investment Manager has waived the External Investment

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Manager's management or incentive fees after December 31, 2013 and, as a result, the External Investment Manager began accruing such fees on January 1, 2014.

CRITICAL ACCOUNTING POLICIES

Basis of Presentation

        Our financial statements are prepared in accordance with generally accepted accounting principles in the United States of America ("U.S. GAAP"). For the years ended December 31, 2013, 2012 and 2011 and as of December 31, 2013 and 2012, our consolidated financial statements include the accounts of MSCC and its consolidated subsidiaries (as noted above and as discussed in detail below, beginning April 1, 2013, the consolidated subsidiaries include the Internal Investment Manager which was previously treated as a portfolio investment). The Investment Portfolio, as used herein, refers to all of our investments in LMM portfolio companies, investments in Middle Market portfolio companies, Other Portfolio investments, investment in the External Investment Manager and investment in the Internal Investment Manager (for all periods up to and including March 31, 2013) but excludes all "Marketable securities and idle funds investments", and, for all periods after March 31, 2013, the Investment Portfolio also excludes the Internal Investment Manager (see Note C—Fair Value Hierarchy for Investments and Debentures—Portfolio Investment Composition for additional discussion of our Investment Portfolio and definitions for the terms LMM, Middle Market, Private Loan and Other Portfolio). For all periods up to and including the period ending March 31, 2013, the Internal Investment Manager was accounted for as a portfolio investment (see Note D) and was not consolidated with MSCC and its consolidated subsidiaries. For all periods after March 31, 2013, the Internal Investment Manager is consolidated with MSCC and its other consolidated subsidiaries. "Marketable securities and idle funds investments" are classified as financial instruments and are reported separately on our Consolidated Balance Sheets and Consolidated Schedule of Investments due to the nature of such investments (see Note B.11.). Our results of operations and cash flows for the years ended December 31, 2013, 2012 and 2011 and financial position as of December 31, 2013 and 2012, are presented on a consolidated basis. The effects of all intercompany transactions between us and our consolidated subsidiaries have been eliminated in consolidation. Certain reclassifications have been made to prior period balances to conform with the current presentation, including certain investments previously included as part of the LMM portfolio or Middle Market portfolio that are now classified as part of the Private Loan portfolio, the reclassification of Investment Portfolio and Marketable securities and idle funds investment related activity from cash flows from investing activities to cash flows from operating activities and the reclassification of certain amounts between accumulated net realized gain from investments and accumulated net investment income.

        Under the investment company rules and regulations pursuant to Article 6 of Regulation S-X and the Audit and Accounting Guide for Investment Companies issued by the American Institute of Certified Public Accountants (the "AICPA Guide"), we are precluded from consolidating portfolio company investments, including those in which we have a controlling interest, unless the portfolio company is another investment company. An exception to this general principle in the AICPA Guide occurs if we hold a controlling interest in an operating company that provides all or substantially all of its services directly to us, or to an investment company of ours. None of the portfolio investments made by us qualify for this exception, including the investment in the External Investment Manager, except as discussed below with respect to the Internal Investment Manager. Therefore, the Investment Portfolio is carried on the balance sheet at fair value, with any adjustments to fair value recognized as "Net Change in Unrealized Appreciation (Depreciation)" on our Statement of Operations until the investment is realized, usually upon exit, resulting in any gain or loss being recognized as a "Net Realized Gain (Loss) from Investments." For all periods prior to and including March 31, 2013, the Internal Investment Manager was accounted for as a portfolio investment and included as part of the Investment Portfolio in our consolidated financial statements. The Internal Investment Manager was

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consolidated with MSCC and its other consolidated subsidiaries prospectively beginning April 1, 2013 as the controlled operating subsidiary began providing substantially all of its services directly or indirectly to Main Street or its portfolio companies.

Portfolio Investment Valuation

        The most significant determination inherent in the preparation of our consolidated financial statements is the valuation of our Investment Portfolio and the related amounts of unrealized appreciation and depreciation. As of December 31, 2013 and 2012, approximately 95% and 89% of our total assets at each date represented our Investment Portfolio valued at fair value. We are required to report our investments at fair value. We follow the provisions of the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("Codification" or "ASC") 820, Fair Value Measurements and Disclosures ("ASC 820"). ASC 820 defines fair value, establishes a framework for measuring fair value, establishes a fair value hierarchy based on the quality of inputs used to measure fair value, and enhances disclosure requirements for fair value measurements.

        Our business strategy calls for us to invest primarily in illiquid debt and equity securities issued by private, LMM companies and debt securities issued by Middle Market companies that are generally larger in size than the LMM companies. We also categorize some of our investments in LMM companies and Middle Market companies as Private Loan portfolio investments, which are typically debt securities issued by companies that are consistent in size with either the LMM companies or Middle Market companies, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. Our portfolio also includes Other Portfolio investments which primarily consist of investments which are not consistent with the typical profiles for our LMM portfolio investments, Middle Market portfolio investments or Private Loan portfolio investments, including investments which may be managed by third parties. All of these portfolio investments may be subject to restrictions on resale.

        LMM investments and Other Portfolio investments generally have no established trading market while Middle Market securities generally have established markets that are not active. Private Loan investments may include investments which have no established trading market or have established markets that are not active. We determine in good faith the fair value of our Investment Portfolio pursuant to a valuation policy in accordance with ASC 820 and a valuation process approved by our Board of Directors and in accordance with the 1940 Act. Our valuation policy and process is intended to provide a consistent basis for determining the fair value of our portfolio.

        For LMM portfolio investments, we generally review external events, including private mergers, sales and acquisitions involving comparable companies, and include these events in the valuation process. For Middle Market portfolio investments, we primarily use observable inputs such as quoted prices in the valuation process. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we generally use either unobservable inputs through obtaining third party quotes or other independent pricing or an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        For valuation purposes, "control" LMM portfolio investments are composed of debt and equity securities in companies for which we have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Market quotations are generally not readily available for our control LMM portfolio investments. As a result, for control LMM portfolio investments, we generally determine the fair value using a combination of market and income approaches. Under the market approach, we will typically use the enterprise value methodology to determine the fair value of these investments. The enterprise value is the fair value at which an enterprise could be sold in a transaction between two willing parties, other than through a forced or liquidation sale. Typically, private companies are bought and sold based on multiples of earnings before

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interest, taxes, depreciation and amortization, or EBITDA, cash flows, net income, revenues, or in limited cases, book value. There is no single methodology for estimating enterprise value. For any one portfolio company, enterprise value is generally described as a range of values from which a single estimate of enterprise value is derived. In estimating the enterprise value of a portfolio company, we analyze various factors, including the portfolio company's historical and projected financial results. We allocate the enterprise value to investments in order of the legal priority of the various components of the portfolio company's capital structure. We will also use the income approach to determine the fair value of these securities, based on projections of the discounted future free cash flows that the portfolio company or the debt security will likely generate, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments. The valuation approaches for our control LMM portfolio investments estimate the value of the investment if we were to sell, or exit, the investment. In addition, these valuation approaches consider the value associated with our ability to control the capital structure of the portfolio company, as well as the timing of a potential exit.

        For valuation purposes, "non-control" LMM portfolio investments are generally composed of debt and equity securities in companies for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Market quotations are generally not readily available for non-control LMM portfolio investments. For our non-control LMM portfolio investments, we typically use a combination of the market and income approaches to value our equity investments and the income approach to value our debt investments similar to the approaches used for our control LMM portfolio investments, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments. Our estimate of the expected repayment date of a LMM debt security is generally the legal maturity date of the instrument, as we generally intend to hold our LMM loans and debt securities to maturity. The yield-to-maturity analysis considers changes in leverage levels, credit quality, portfolio company performance and other factors. We will use the value determined by the yield-to-maturity analysis as the fair value for that security; however, because of our general intent to hold our loans to maturity, the fair value will not exceed the principal amount of the LMM debt security. A change in the assumptions that we use to estimate the fair value of our LMM debt securities using the yield-to-maturity analysis could have a material impact on the determination of fair value. If there is deterioration in credit quality or if a LMM debt security is in workout status, we may consider other factors in determining the fair value of the LMM debt security, including the value attributable to the debt security from the enterprise value of the portfolio company or the proceeds that would most likely be received in a liquidation analysis.

        Our Middle Market portfolio investments primarily consist of direct investments in or secondary purchases of interest-bearing debt securities in companies that are generally larger in size than the LMM companies included in our Investment Portfolio. For valuation purposes, all of our Middle Market portfolio investments are non-control investments for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. We primarily use observable inputs to determine the fair value of these investments through obtaining third party quotes or other independent pricing, to the extent such sufficient observable inputs are available to determine fair value. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we generally use either unobservable inputs through obtaining third party quotes or other independent pricing or an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

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        Our Private Loan portfolio investments primarily consist of direct investments in or secondary purchases of interest-bearing debt securities in companies that are consistent with the size of companies included in our LMM portfolio or our Middle Market portfolio. For valuation purposes, all of our Private Loan portfolio investments are non-control investments for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. As sufficient observable inputs to determine the fair value of these Private Loan portfolio investments through obtaining third party pricing or other independent pricing are not generally available, we generally use either unobservable inputs through obtaining third party quotes or other independent pricing or an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        For valuation purposes, all of our Other Portfolio investments are non- control investments for which we generally do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Our Other Portfolio investments comprised 3.3% and 2.6%, respectively, of our Investment Portfolio at fair value as of December 31, 2013 and 2012. Similar to the LMM investment portfolio, market quotations for Other Portfolio equity investments are generally not readily available. For our Other Portfolio equity investments, we determine the fair value based on the fair value of the portfolio company as determined by independent third parties and based on our proportional ownership in the portfolio company, as well as the financial position and assessed risk of each of these portfolio investments. For Other Portfolio debt investments with observable inputs, we determine the fair value of these investments through obtaining third party quotes or other independent pricing, to the extent such sufficient observable inputs are available to determine fair value. To the extent observable inputs are not available, we value these Other Portfolio debt investments through an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        For valuation purposes, our investment in the External Investment Manager is a control investment for which we have a controlling interest in the portfolio company and the ability to nominate a majority of the portfolio company's board of directors. Market quotations are not readily available for this investment, and as a result, we determine the fair value of the External Investment Manager using the enterprise value methodology under the market approach. In estimating the enterprise value, we analyze various factors, including the entity's historical and projected financial results, as well as its size, marketability and performance relative to the population of market multiples. This valuation approach estimates the value of the investment if we were to sell, or exit, the investment. In addition, we consider the value associated with our ability to control the capital structure of the company, as well as the timing of a potential exit.

        Due to the inherent uncertainty in the valuation process, our determination of fair value for our Investment Portfolio may differ materially from the values that would have been used had a ready market for the securities existed. In addition, changes in the market environment, portfolio company performance and other events that may occur over the lives of the investments may cause the gains or losses ultimately realized on these investments to be materially different than the valuations currently assigned. We determine the fair value of each individual investment and record changes in fair value as unrealized appreciation or depreciation.

Revenue Recognition

Interest and Dividend Income

        We record interest and dividend income on the accrual basis to the extent amounts are expected to be collected. Dividend income is recorded as dividends are declared by the portfolio company or at the point an obligation exists for the portfolio company to make a distribution. In accordance with our valuation policy, we evaluate accrued interest and dividend income periodically for collectability. When

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a loan or debt security becomes 90 days or more past due, and if we otherwise do not expect the debtor to be able to service all of its debt or other obligations, we will generally place the loan or debt security on non-accrual status and cease recognizing interest income on that loan or debt security until the borrower has demonstrated the ability and intent to pay contractual amounts due. If a loan or debt security's status significantly improves regarding the debtor's ability to service the debt or other obligations, or if a loan or debt security is fully impaired, sold or written off, we will remove it from non-accrual status.

Fee Income

        We may periodically provide services, including structuring and advisory services, to our portfolio companies or other third parties. For services that are separately identifiable and evidence exists to substantiate fair value, income is recognized as earned, which is generally when the investment or other applicable transaction closes. Fees received in connection with debt financing transactions for services that do not meet these criteria are treated as debt origination fees and are deferred and accreted into interest income over the life of the financing.

Payment-in-Kind ("PIK") Interest and Cumulative Dividends

        We hold debt and preferred equity instruments in our Investment Portfolio that contain payment-in-kind ("PIK") interest and cumulative dividend provisions. The PIK interest, computed at the contractual rate specified in each debt agreement, is periodically added to the principal balance of the debt and is recorded as interest income. Thus, the actual collection of this interest may be deferred until the time of debt principal repayment. Cumulative dividends are recorded as dividend income, and any dividends in arrears are added to the balance of the preferred equity investment. The actual collection of these dividends in arrears may be deferred until such time as the preferred equity is redeemed. To maintain RIC tax treatment (as discussed below), these non-cash sources of income may need to be paid out to stockholders in the form of distributions, even though we may not have collected the PIK interest and cumulative dividends in cash. We will stop accruing PIK interest and cumulative dividends and will write off any accrued and uncollected interest and dividends in arrears when it is determined that such PIK interest and dividends in arrears are no longer collectible.

Share-Based Compensation

        We account for our share-based compensation plans using the fair value method, as prescribed by ASC 718, Compensation—Stock Compensation. Accordingly, for restricted stock awards, we measured the grant date fair value based upon the market price of our common stock on the date of the grant and will amortize this fair value to share-based compensation expense over the requisite service period or vesting term.

Income Taxes

        MSCC has elected to be treated for federal income tax purposes as a RIC. As a RIC, MSCC generally will not pay corporate-level federal income taxes on any net ordinary income or capital gains that MSCC distributes to its stockholders as dividends. MSCC must generally distribute at least 90% of its investment company taxable income to qualify for pass-through tax treatment and maintain its RIC status. As part of maintaining RIC status, undistributed taxable income (subject to a 4% excise tax) pertaining to a given fiscal year may be distributed up to 12 months subsequent to the end of that fiscal year, provided such dividends are declared prior to the filing of the federal income tax return for the applicable fiscal year.

        The Taxable Subsidiaries hold certain portfolio investments for us. The Taxable Subsidiaries are consolidated with us for financial reporting purposes, and the portfolio investments held by the Taxable

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Subsidiaries are included in our consolidated financial statements. The principal purpose of the Taxable Subsidiaries is to permit us to hold equity investments in portfolio companies which are "pass through" entities for tax purposes and continue to comply with the "source income" requirements contained in the RIC tax provisions of the Code. The Taxable Subsidiaries are not consolidated with us for income tax purposes and may generate income tax expense, or benefit, and the related tax assets and liabilities, as a result of their ownership of certain portfolio investments. This income tax expense, or benefit, if any, and related tax assets and liabilities, are reflected in our consolidated financial statements.

        The Internal Investment Manager has elected, for tax purposes, to be treated as a taxable entity, is not consolidated with us for income tax purposes and is taxed at normal corporate tax rates based on its taxable income, or loss, and, as a result of its activities, may generate income tax expense or benefit. The Internal Investment Manager elected to be treated as a taxable entity to enable it to receive fee income and to allow MSCC to continue to comply with the "source income" requirements contained in the RIC tax provisions of the Code. The taxable income, or loss, of the Internal Investment Manager may differ from its book income, or loss, due to temporary book and tax timing differences and permanent differences. Through March 31, 2013, the Internal Investment Manager provided for any income tax expense, or benefit, and any related tax assets or liabilities, in its separate financial statements. Beginning April 1, 2013, the Internal Investment Manager is included in our consolidated financial statements and reflected as a consolidated subsidiary and any income tax expense, or benefit, and any related tax assets and liabilities, are reflected in our consolidated financial statements.

        The Taxable Subsidiaries and the Internal Investment Manager use the liability method in accounting for income taxes. Deferred tax assets and liabilities are recorded for temporary differences between the tax basis of assets and liabilities and their reported amounts in the financial statements, using statutory tax rates in effect for the year in which the temporary differences are expected to reverse. A valuation allowance is provided against deferred tax assets when it is more likely than not that some portion or all of the deferred tax asset will not be realized.

        Taxable income generally differs from net income for financial reporting purposes due to temporary and permanent differences in the recognition of income and expenses. Taxable income generally excludes net unrealized appreciation or depreciation, as investment gains or losses are not included in taxable income until they are realized.

INVESTMENT PORTFOLIO COMPOSITION

        LMM portfolio investments principally consist of secured debt, equity warrants and direct equity investments in privately held, LMM companies based in the United States. The LMM debt investments are primarily secured by either a first or second lien on the assets of the portfolio company, generally bear interest at fixed rates, and generally mature between five and seven years from the original investment date. In most LMM portfolio companies, we also receive nominally priced equity warrants and/or make direct equity investments, usually in connection with a debt investment.

        Middle Market portfolio investments primarily consist of direct investments in or secondary purchases of interest-bearing debt securities in privately held companies based in the United States that are generally larger in size than the LMM companies included in our LMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien and typically have a term of between three and five years.

        Our Private Loan portfolio investments primarily consist of investments in interest-bearing debt securities in companies that are consistent with the size of companies included in our LMM portfolio or our Middle Market portfolio. Our Private Loan portfolio debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have a term of between three and seven years.

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        Our Other Portfolio investments primarily consist of investments which are not consistent with the typical profiles for our LMM, Middle Market or Private Loan portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds. As of December 31, 2013, we had Other Portfolio investments in six companies, collectively totaling approximately $42.8 million in fair value and approximately $40.1 million in cost basis and which comprised 3.3% of our Investment Portfolio at fair value as of December 31, 2013.

        Our external asset management business is conducted through our External Investment Manager. We have entered into an agreement through the Internal Investment Manager to provide the External Investment Manager with asset management service support for HMS Income Fund, Inc. ("HMS Income"). Through this agreement, we provide management and other services to the External Investment Manager, as well as access to our employees, infrastructure, business relationships, management expertise and capital raising capabilities. Beginning in the first quarter of 2014, we charge the External Investment Manager a fee for the use of these services. The External Investment Manager earns management fees based on the assets of the funds under management and may earn incentive fees, or a carried interest, based on the performance of the funds managed.

        The following tables summarize the composition of our total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments at cost and fair value by type of investment as a percentage of the total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments as of December 31, 2013 and 2012 (this information excludes the Other Portfolio investments, the External Investment Manager and the Internal Investment Manager).

 

        The following tables summarize the composition of the total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments by geographic region of the United States or other countries at cost and fair value as a percentage of the total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments, as of December 31, 2013 and 2012 (this information excludes the Other Portfolio

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investments, the External Investment Manager and the Internal Investment Manager). The geographic composition is determined by the location of the corporate headquarters of the portfolio company.

 

        Our LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments are in companies conducting business in a variety of industries. The following tables summarize the composition of our total combined LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments, by industry at cost and fair value as of

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December 31, 2013 and 2012 (this information excludes the Other Portfolio investments, the External Investment Manager and the Internal Investment Manager).

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        Our LMM portfolio investments, Middle Market portfolio investments and Private Loan portfolio investments carry a number of risks including, but not limited to: (1) investing in companies which may have limited operating histories and financial resources; (2) holding investments that generally are not publicly traded and which may be subject to legal and other restrictions on resale; and (3) other risks common to investing in below investment grade debt and equity investments in our Investment Portfolio. Please see "Risk Factors—Risks Related to Our Investments" in this prospectus supplement and the accompanying prospectus for a more complete discussion of the risks involved with investing in our Investment Portfolio.

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PORTFOLIO ASSET QUALITY

        We utilize an internally developed investment rating system to rate the performance of each LMM portfolio company and to monitor our expected level of returns on each of our LMM investments in relation to our expectations for the portfolio company. The investment rating system takes into consideration various factors, including but not limited to each investment's expected level of returns and the collectability of our debt investments, comparisons to competitors and other industry participants and the portfolio company's future outlook.

•

Investment Rating 1 represents a LMM portfolio company that is performing in a manner which significantly exceeds expectations.



•

Investment Rating 2 represents a LMM portfolio company that, in general, is performing above expectations.



•

Investment Rating 3 represents a LMM portfolio company that is generally performing in accordance with expectations.



•

Investment Rating 4 represents a LMM portfolio company that is underperforming expectations. Investments with such a rating require increased monitoring and scrutiny by us.



•

Investment Rating 5 represents a LMM portfolio company that is significantly underperforming. Investments with such a rating require heightened levels of monitoring and scrutiny by us and involve the recognition of significant unrealized depreciation on such investment.

        All new LMM portfolio investments receive an initial Investment Rating of 3.

        The following table shows the distribution of our LMM portfolio investments on the 1 to 5 investment rating scale at fair value as of December 31, 2013 and 2012.

        Based upon our investment rating system, the weighted average rating of our LMM portfolio was approximately 2.2 as of December 31, 2013 and 2.1 as of December 31, 2012.

        For the total Investment Portfolio, as of December 31, 2013, we had two investments with positive fair value on non-accrual status which comprised approximately 2.3% of the total Investment Portfolio at fair value and 4.7% of the total Investment Portfolio at cost and no fully impaired investments. For the total Investment Portfolio, as of December 31, 2012, we had no investments with positive fair value on non-accrual status and one fully impaired investment which comprised approximately 0.2% of the total portfolio investments at cost, excluding the investment in the affiliated Internal Investment Manager.

        The broader fundamentals of the United States economy remain mixed, and unemployment remains elevated. In the event that the United States economy contracts, it is likely that the financial results of small- to mid-sized companies, like those in which we invest, could experience deterioration or limited growth from current levels, which could ultimately lead to difficulty in meeting their debt

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service requirements and an increase in defaults. Consequently, we can provide no assurance that the performance of certain portfolio companies will not be negatively impacted by economic cycles or other conditions, which could also have a negative impact on our future results.

DISCUSSION AND ANALYSIS OF RESULTS OF OPERATIONS

Comparison of years ended December 31, 2013 and 2012

 

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Investment Income

        For the year ended December 31, 2013, total investment income was $116.5 million, a 29% increase over the $90.5 million of total investment income for the corresponding period of 2012. This comparable period increase was principally attributable to (i) a $22.4 million increase in interest income from higher average levels of portfolio debt investments and increased activity in the Investment Portfolio and (ii) a $3.9 million increase in dividend income from Investment Portfolio equity investments, partially offset by a $0.3 million decrease in interest and dividend income from Marketable securities and idle funds investments. The $26.0 million increase in investment income in the year ended December 31, 2013 includes a $1.7 million decrease in the amount of non-recurring investment income associated with debt repayment and financing activities of LMM portfolio investments included in investment income, partially offset by a $1.1 million increase in the amount of investment income related to higher accelerated prepayment and repricing activity of certain Middle Market and Private Loan portfolio debt investments and Marketable securities and idle funds investments in each case for the year ended December 31, 2013, when compared to the same period in 2012.

Expenses

        For the year ended December 31, 2013, total expenses increased to $41.1 million from $31.2 million for the corresponding period of 2012. This comparable period increase in expenses was principally attributable to (i) a $4.6 million increase in interest expense, (ii) higher compensation and related expenses of $2.1 million, primarily as a result of additional personnel compared to the same period in the prior year, (iii) a $1.6 million increase in other general and administrative expenses and (iv) an increase of $1.6 million in share-based compensation, primarily due to $1.3 million of expense associated with the accelerated vesting of all the unvested shares of restricted stock in connection with the retirement of our former Executive Vice Chairman during the year ended December 31, 2013. The $4.6 million increase in interest expense was primarily a result of (i) a $4.4 million increase primarily related to the issuance of the 6.125% Notes ("the Notes") in April 2013 and (ii) a $1.3 million increase related to a higher average outstanding balance on the Credit Facility, partially offset by a $1.1 million decrease related to prepayments on our Small Business Investment Company ("SBIC") debentures and lower average interest rates on the SBIC debentures. The ratio of our total operating expenses, excluding interest expense and excluding the effect of the accelerated vesting of restricted stock of our former Executive Vice Chairman discussed above, as a percentage of our average total assets was 1.7% for the year ended December 31, 2013, compared to 1.8% for the prior year. Including the effect of the accelerated vesting of restricted stock of our former Executive Vice Chairman, the ratio would have been 1.8% for the year ended December 31, 2013.

Distributable Net Investment Income

        Distributable net investment income increased $17.7 million to $79.6 million, or $2.17 per share, compared with $61.9 million, or $2.09 per share, in the corresponding period of 2012. The increase in

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distributable net investment income was primarily due to the higher level of total investment income partially offset by higher interest and other operating expenses, due to the changes discussed above. The distributable net investment income on a per share basis for the year ended December 31, 2013 reflects the impact of a greater number of average shares outstanding compared to the corresponding period in 2012 primarily due to the June 2012, December 2012 and August 2013 follow-on equity offerings.

Net Investment Income

        Net investment income for the year ended December 31, 2013 was $75.4 million, or a 27% increase, compared to net investment income of $59.3 million for the corresponding period of 2012. The increase in net investment income was principally attributable to the increase in total investment income partially offset by higher interest and other operating expenses as discussed above.

Distributable Net Realized Income

        Distributable net realized income was $82.1 million, or $2.24 per share, for the year ended December 31, 2013 compared with $78.4 million, or $2.65 per share, in the corresponding period of 2012. The $3.7 million increase was primarily attributable to higher distributable net investment income in the year ended December 31, 2013 compared to the corresponding period of 2012 as discussed above, partially offset by (i) a decrease in net realized gain from investments of $9.2 million, to $7.3 million in 2013 from $16.5 million in prior year, and (ii) a realized loss of $4.8 million on the repayment of certain SBIC debentures issued to MSC II which had been accounted for on the fair value method of accounting under ASC 825. The $7.3 million net realized gain on investments during the year ended December 31, 2013 was primarily attributable to (i) a realized gain of $11.3 million on the full exit of two LMM equity investments, (ii) realized gains of $1.0 million on the partial exits of several LMM investments, (iii) net realized gains on several Middle Market and Marketable securities and idle funds investments totaling $1.9 million, partially offset by (i) realized losses of $2.6 million on the restructuring of a LMM equity investment and 1.8 million on the full exit of one LMM investment, respectively, and (ii) the realized loss of $1.8 million on the full exit of one Middle Market investment.

Net Realized Income

        The lower net realized gain from investments and the realized loss from the SBIC debentures, partially offset by the higher net investment income, in the year ended December 31, 2013 compared to the corresponding period of 2012, in each case as discussed above, resulted in a $2.1 million increase in net realized income compared with the corresponding period of 2012.

Net Increase in Net Assets Resulting from Operations Attributable to Common Stock

        The net increase in net assets resulting from operations attributable to common stock during the year ended December 31, 2013 was $96.9 million, or $2.65 per share, compared with $104.4 million, or $3.53 per share, in the corresponding period of 2012. This $7.5 million decrease from the comparable period in the prior year was primarily the result of the $20.5 million difference in the net change in unrealized appreciation to $19.0 million for the year ended December 31, 2013, compared to $39.5 million for the comparable period in the prior year, partially offset by (i) a $10.8 million decrease in the net income tax provision and (ii) the $2.1 million increase in net realized income due to the factors discussed above, both for the year ended December 31, 2013 in comparison to the comparable period in the prior year. The total net change in unrealized appreciation for the year ended December 31, 2013 of $19.0 million included (i) $16.2 million of net unrealized appreciation from portfolio investments and (ii) the net unrealized appreciation of $4.4 million on the SBIC debentures, which resulted from the $4.8 million of accounting reversals of prior unrealized depreciation on the SBIC debentures in conjunction with the realized loss on the repayment of the SBIC debentures as

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discussed above, partially offset by net unrealized depreciation of $0.4 million on the remaining SBIC debentures held by MSC II, partially offset by the net unrealized depreciation from Marketable securities and idle funds investments of $1.7 million. The $16.2 million net change in unrealized appreciation from portfolio investments for the year ended December 31, 2013 was principally attributable to (i) unrealized appreciation on 37 LMM portfolio investments totaling $60.6 million, partially offset by unrealized depreciation on 15 LMM portfolio investments totaling $38.8 million, (ii) $3.7 million of net unrealized appreciation on Middle Market investments, (iii) $1.1 million of net unrealized appreciation on the External Investment Manager and (iv) $2.2 million of net unrealized appreciation on the Other Portfolio investments, partially offset by accounting reversals of net unrealized appreciation from prior periods of $12.8 million related to portfolio investment exits and repayments. The net income tax benefit for the year ended December 31, 2013 related to a deferred tax benefit of $3.6 million, partially offset by an income tax provision on other taxes of $3.6 million. The deferred taxes related primarily to net unrealized depreciation on equity investments held in our Taxable Subsidiaries. The other taxes include $1.8 million related to an accrual for excise tax on our estimated spillover taxable income and $1.8 million related to accruals for state and other taxes.

Comparison of years ended December 31, 2012 and December 31, 2011

 

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Investment Income

        For the year ended December 31, 2012, total investment income was $90.5 million, a $24.3 million, or 37%, increase over the $66.2 million for the corresponding period of 2011. This comparable period increase was principally attributable to (i) a $19.1 million increase in interest income from increased activity in the investment portfolio and higher average levels of portfolio debt investments and interest-bearing marketable securities investments, (ii) a $3.2 million increase in dividend income from portfolio equity investments and (iii) a $2.0 million increase in fee income due to the increased activity in and size of the investment portfolio. The increase in investment income included (i) $1.8 million of non-recurring investment income during the first quarter of 2012 associated with repayment and financing activities for two LMM portfolio investments, (ii) a $3.2 million increase in investment income associated with higher levels of accelerated prepayment activity for certain Middle Market portfolio debt investments and marketable securities investments in comparison to 2011 and (iii) special dividend activity of $1.4 million in the fourth quarter of 2012.

Expenses

        For the year ended December 31, 2012, total expenses increased by approximately $4.3 million, or 16%, to $31.2 million from $26.9 million for the corresponding period of 2011. This comparable period increase in expenses was principally attributable to (i) higher interest expense of $2.1 million as a result of the net issuance of an additional $5 million in SBIC debentures subsequent to December 31, 2011, increased borrowing activity under the Credit Facility and higher unused fees associated with the increased commitments under the Credit Facility, (ii) higher share-based compensation expense of $0.5 million related to non-cash amortization for restricted share grants, and (iii) higher compensation and expenses of $1.7 million related to increases in personnel and incentive compensation compared to the corresponding period of 2011. For the years ended December 31, 2012 and 2011, the ratio of our total operating expenses, excluding interest expense, as a percentage of our quarterly average total assets was 1.8% and 2.2%, respectively.

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Distributable Net Investment Income

        Distributable net investment income for the year ended December 31, 2012 increased to $61.9 million, or $2.09 per share, compared with distributable net investment income of $41.3 million, or $1.77 per share, for the corresponding period of 2011. The increase in distributable net investment income was primarily due to the higher level of total investment income partially offset by higher interest and other operating expenses, due to the changes discussed above. Distributable net investment income on a per share basis for the year ended 2012 reflects (i) an increase of approximately $0.13 per share from 2011 in investment income attributable to higher levels of accelerated prepayment and repricing activity for certain debt investments and marketable securities investments, (ii) approximately $0.05 per share from the special dividend activity in the fourth quarter of 2012 and (iii) a greater number of average shares outstanding compared to the corresponding period in 2011 primarily due to the net effect of December 2012, June 2012, October 2011 and March 2011 follow-on equity offerings.

Net Investment Income

        Net investment income for the year ended December 31, 2012 was $59.3 million, or a 51% increase, compared to net investment income of $39.3 million for the corresponding period of 2011. The increase in net investment income was principally attributable to the increase in total investment income partially offset by higher interest and other operating expenses as discussed above.

Distributable Net Realized Income

        Distributable net realized income increased to $78.4 million, or $2.65 per share, for the year ended 2012 compared with distributable net realized income of $44.0 million, or $1.89 per share, for the corresponding period of 2011. The increase was primarily attributable to the higher level of distributable net investment income and the higher level of total net realized gain from investments in 2012 compared to the corresponding period of 2011. The $16.5 million net realized gain during 2012 was primarily attributable to (i) realized gains recognized on two partial exits of LMM portfolio company equity investments, (ii) a realized gain recognized on the full exit of a LMM portfolio company equity investment and (iii) realized gains related to Middle Market and marketable securities investments, partially offset by (iv) realized losses on the full exits of three LMM portfolio company investments.

Net Realized Income

        The higher level of net investment income and the higher level of total net realized gain from investments in 2012 compared to the corresponding period of 2011, both as discussed above, resulted in a $33.8 million increase in net realized income compared with the corresponding period of 2011.

Net Increase in Net Assets Resulting from Operations

        The net increase in net assets resulting from operations attributable to common stock during the year ended December 31, 2012 was $104.4 million, or $3.53 per share, compared with a net increase of $63.0 million, or $2.76 per share, in 2011. This $41.4 million increase was a result of the increase in net realized income discussed above, plus differences in the net change in unrealized appreciation from portfolio investments, marketable securities, SBIC debentures and investment in the Internal Investment Manager and the difference in the income tax provision. For the year ended December 31, 2012, the $44.5 million net change in unrealized appreciation from portfolio investments was principally attributable to (i) unrealized appreciation on 37 LMM portfolio investments totaling $57.8 million, partially offset by unrealized depreciation on 10 LMM portfolio investments totaling $4.6 million, (ii) $9.7 million of net unrealized appreciation on the Middle Market investment portfolio and (iii) $0.8 million of net unrealized appreciation on the Other Portfolio investments and Marketable

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securities and idle funds investments, partially offset by (iv) accounting reversals of net unrealized appreciation from prior periods of $18.3 million related to portfolio investment exits and repayments, and (v) accounting reversals of net unrealized appreciation from prior periods of $0.5 million related to Marketable securities and idle funds investments exits and repayments. For the year ended December 31, 2012, the $5.0 million net change in unrealized appreciation attributable to SBIC debentures and investment in the Internal Investment Manager was primarily attributable to unrealized depreciation on the SBIC debentures held by MSC II. The noncontrolling interest of $0.1 million recognized during the first quarter of 2012 reflects the pro rata portion of the net increase in net assets resulting from operations for MSC II attributable to the equity interests in MSC II that were not owned by MSCC prior to MSCC's completion of the Final MSC II Exchange. For the year ended December 31, 2012, we also recognized a net income tax provision of $10.8 million related to deferred taxes of $8.0 million and other taxes of $2.8 million. The deferred taxes related primarily to net unrealized appreciation on equity investments held in our taxable subsidiaries. The other taxes include $1.6 million related to an accrual for excise tax on our estimated spillover taxable income as of December 31, 2012 and $1.2 million related to accruals for state and other taxes.

Liquidity and Capital Resources

Cash Flows

        For the year ended December 31, 2013, we experienced a net decrease in cash and cash equivalents in the amount of $28.8 million. During the period, we used $240.7 million of cash for our operating activities, which resulted primarily from (i) cash flows we generated from the ordinary operating profits earned through our operating activities totaling $63.8 million, which is our $79.6 million of distributable net investment income, excluding the non-cash effects of the accretion of unearned income of $10.9 million, payment-in-kind interest income of $5.0 million, cumulative dividends of $1.4 million and the amortization expense for deferred financing costs of $1.5 million, (ii) cash uses totaling $824.8 million from (a) the funding of new portfolio company investments and settlement of accruals for portfolio investments existing as of December 31, 2013, which together total $767.5 million, (b) the funding of new Marketable securities and idle funds investments and settlement of accruals for Marketable securities and idle funds investments existing as of December 31, 2012, which together total $54.0 million, and (c) $3.3 million related to decreases in payables and accruals, and (iii) cash proceeds totaling $520.3 million from (a) $465.0 million in cash proceeds from the repayments or sales of debt investments and sales of equity investments, (b) $51.7 million of cash proceeds from the sale of Marketable securities and idle funds investments and (c) decreases in other assets of $3.6 million. During 2013, $211.9 million in cash was provided by financing activities, which principally consisted of (i) $131.5 million in net cash proceeds from public stock offering in August 2013, (ii) $105.0 million in net cash proceeds from the Credit Facility and (iii) $92.0 million in cash proceeds from the issuance of the Notes, partially offset by (i) a $24.8 million net decrease in outstanding SBIC debentures resulting from $63.8 million in repayments of SBIC debentures, net of $39.0 million in proceeds from the issuance of SBIC debentures, (ii) $83.2 million in cash dividends paid to stockholders and (iii) $6.3 million in loan costs associated with our SBIC debentures, our Notes and the Credit Facility.

        For the year ended December 31, 2012, we experienced a net increase in cash and cash equivalents in the amount of $20.9 million. During that period, we generated $48.9 million of cash from our operating activities, primarily from (i) distributable net investment income, excluding the non-cash effects of the accretion of unearned income, payment in kind interest income and the amortization of deferred financing costs, (ii) increases in payables, and (iii) realized gains, partially offset by increases in interest receivable. We used $184.5 million in net cash from investing activities, principally including the funding of $639.8 million for new portfolio company investments and the funding of $14.4 million for Marketable securities and idle funds investments, partially offset by (i) $400.0 million in cash

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proceeds from the repayment of portfolio debt investments, (ii) $35.1 million in cash proceeds from the exit of portfolio equity investments and (iii) $34.5 million of cash proceeds from the sale of Marketable securities and idle funds investments. During 2012, $156.5 million in cash was provided by financing activities, which principally consisted of (i) $169.9 million in net cash proceeds from public stock offerings in June and December 2012, (ii) $25.0 million in net cash proceeds from the Credit Facility and (iii) $5.0 million in net cash proceeds from the issuance of SBIC debentures, partially offset by (i) $39.9 million in cash dividends paid to stockholders and (ii) $2.2 million in loan costs associated with our SBIC debentures and the Credit Facility.

        For the year ended December 31, 2011, we experienced a net increase in cash and cash equivalents in the amount of $20.3 million. During that period, we generated $37.2 million of cash from our operating activities, primarily from (i) distributable net investment income, excluding the non-cash effects of the accretion of unearned income, payment-in-kind interest income and the amortization of deferred financing costs, (ii) increases in payables, and (iii) realized gains, partially offset by (iv) increases in interest receivable. We used $220.5 million in net cash from investing activities, principally including (i) the funding of $358.9 million for new portfolio company investments and (ii) the funding of $33.5 million for Marketable securities and idle funds investments, partially offset by (i) $160.2 million in cash proceeds from the repayment of portfolio debt investments and from the exit of portfolio equity investments and (ii) $11.7 million of cash proceeds from the sale of Marketable securities and idle funds investments. During 2011, $203.6 million in cash was provided by financing activities, which principally consisted of (i) $127.8 million in net cash proceeds from public stock offerings in March 2011 and October 2011, (ii) $40.0 million in cash proceeds from the issuance of SBIC debentures, and (iii) $68.0 million in net cash proceeds from the Credit Facility, partially offset by $28.3 million in cash dividends paid to stockholders and $2.3 million in loan costs associated with our SBIC debentures and credit facility.

Capital Resources

        As of December 31, 2013, we had $34.7 million in cash and cash equivalents, $13.3 million in Marketable securities and idle funds investments and $208.0 million of unused capacity under the Credit Facility, which we maintain to support our future investment and operating activities. As of December 31, 2013, our net asset value totaled $792.5 million, or $19.89 per share.

        The Credit Facility was amended and restated during the year ended December 31, 2013 to provide for an increase in total commitments from $287.5 million to $445.0 million and to increase the diversified group of lenders to thirteen lenders. The Credit Facility contains an accordion feature which allows us to increase the total commitments under the facility up to $500 million from new or existing lenders on the same terms and conditions as the existing commitments.

        Borrowings under the Credit Facility bear interest, subject to our election, on a per annum basis equal to (i) the applicable LIBOR rate (0.17%, as of December 31, 2013) plus 2.25% or (ii) the applicable base rate (Prime Rate, 3.25% as of December 31, 2013) plus 1.25%. We pay unused commitment fees of 0.25% per annum on the unused lender commitments under the Credit Facility. The Credit Facility is secured by a first lien on the assets of MSCC and its subsidiaries, excluding the assets of the Funds. The Credit Facility contains certain affirmative and negative covenants, including but not limited to: (i) maintaining a minimum availability of at least 10% of the borrowing base, (ii) maintaining an interest coverage ratio of at least 2.0 to 1.0, (iii) maintaining an asset coverage ratio of at least 1.5 to 1.0, and (iv) maintaining a minimum tangible net worth. The Credit Facility is now provided on a revolving basis through the maturity date in September 2018, and contains two, one-year extension options which could extend the final maturity by up to two years, subject to certain conditions, including lender approval. At December 31, 2013, we had $237.0 million in borrowings outstanding under the Credit Facility. As of December 31, 2013, the interest rate on the Credit Facility was 2.4%, and we were in compliance with all financial covenants of the Credit Facility.

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        Due to each of the Funds' status as a licensed SBIC, we have the ability to issue, through the Funds, debentures guaranteed by the SBA at favorable interest rates. Under the regulations applicable to SBIC funds, an SBIC can have outstanding debentures guaranteed by the SBA generally in an amount up to twice its regulatory capital, which effectively approximates the amount of its equity capital. Debentures guaranteed by the SBA have fixed interest rates that equal prevailing 10-year Treasury Note rates plus a market spread and have a maturity of ten years with interest payable semi-annually. The principal amount of the debentures is not required to be paid before maturity but may be pre-paid with no prepayment penalty. During the year ended December 31, 2013, we voluntarily prepaid $63.8 million of our SBIC debentures as part of an effort to manage the maturity dates of our oldest SBIC debentures. Main Street expects to issue new SBIC debentures under the SBIC program in the future in an amount up to the regulatory maximum amount of $225.0 million. On December 31, 2013, we, through the Funds, had $200.2 million of outstanding indebtedness guaranteed by the SBA, which carried a weighted average annual fixed interest rate of approximately 3.8%. The first maturity related to the SBIC debentures does not occur until 2017, and the remaining weighted average duration is approximately 7.3 years as of December 31, 2013.

        In April, 2013, we issued $92.0 million, including the underwriter's full exercise of the over-allotment option, in aggregate principal amount of the Notes. The Notes are unsecured obligations and rank pari passu with our current and future senior unsecured indebtedness; senior to any of our future indebtedness that expressly provides it is subordinated to the Notes; effectively subordinated to all of our existing and future secured indebtedness, to the extent of the value of the assets securing such indebtedness, including borrowings under our Credit Facility; and structurally subordinated to all existing and future indebtedness and other obligations of any of our subsidiaries, including without limitation, the indebtedness of the Funds. The Notes mature on April 1, 2023, and may be redeemed in whole or in part at any time or from time to time at our option on or after April 1, 2018. We may from time to time repurchase Notes in accordance with the 1940 Act and the rules promulgated thereunder. During the year ended December 31, 2013, we repurchased $1.1 million principal of the Notes in the open market for an aggregate purchase price of $1.1 million and surrendered them to the Trustee for cancellation. As of December 31, 2013, the outstanding balance of the Notes was $90.9 million. The indenture governing the Notes ("the Notes Indenture") contains certain covenants, including covenants requiring our compliance with (regardless of whether we are subject to) the asset coverage requirements set forth in Section 18(a)(1)(A) as modified by Section 61(a)(1) of the 1940 Act, as well as covenants requiring us to provide financial information to the holders of the Notes and the Trustee if we cease to be subject to the reporting requirements of the Securities Exchange Act of 1934. These covenants are subject to limitations and exceptions that are described in the Notes Indenture.

        In June 2012, we completed a follow-on public stock offering in which we sold 4,312,500 shares of common stock, including the underwriters' full exercise of the over-allotment option, at a price to the public of $22.50 per share (or approximately 143% of the then latest reported Net Asset Value per share), resulting in total net proceeds of approximately $93.0 million, after deducting underwriters' commissions and offering costs. In December 2012, we completed a follow-on public stock offering in which we sold 2,875,000 shares of common stock, including the underwriters' full exercise of the over-allotment option, at a price to the public of $28.00 per share (or approximately 160% of the then latest reported Net Asset Value per share), resulting in total net proceeds of approximately $77.1 million, after deducting underwriters' commissions and offering costs. In August 2013, we completed a follow-on public equity offering of 4,600,000 shares of common stock, including the underwriters' full exercise of their option to purchase additional shares, at a price to the public of $29.75 per share (or approximately 159% of the then latest reported Net Asset Value per share), resulting in total net proceeds of approximately $131.5 million, after deducting underwriters' commissions and offering costs.

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        We anticipate that we will continue to fund our investment activities through existing cash and cash equivalents, the liquidation of Marketable securities and idle funds investments, and a combination of future debt and equity capital. Our primary uses of funds will be investments in portfolio companies, operating expenses and cash distributions to holders of our common stock.

        We periodically invest excess cash balances into Marketable securities and idle funds investments. The primary investment objective of Marketable securities and idle funds investments is to generate incremental cash returns on excess cash balances prior to utilizing those funds for investment in our LMM, Middle Market and Private Loan portfolio investments. Marketable securities and idle funds investments generally consist of debt investments, independently rated debt investments, certificates of deposit with financial institutions, diversified bond funds and publicly traded debt and equity investments. The composition of Marketable securities and idle funds investments will vary in a given period based upon, among other things, changes in market conditions, the underlying fundamentals in our Marketable securities and idle funds investments, our outlook regarding future LMM, Middle Market and Private Loan portfolio investment needs, and any regulatory requirements applicable to us.

        If our common stock trades below our net asset value per share, we will generally not be able to issue additional common stock at the market price unless our stockholders approve such a sale and our Board of Directors makes certain determinations. We did not seek approval to sell shares of our common stock below the then current net asset value per share of our common stock from our stockholders at our 2013 annual meeting of stockholders because our common stock price per share had been trading significantly above the current net asset value per share of our common stock, and we do not currently expect to seek such approval at our 2014 annual meeting of stockholders for the same reason. We would therefore need future approval from our stockholders to issue shares below the then current net asset value per share if we desire to issue shares of our common stock at a price below the then current net asset value per share.

        In order to satisfy the Code requirements applicable to a RIC, we intend to distribute to our stockholders, after consideration and application of our ability under the Code to spillover certain excess undistributed taxable income from one tax year into the next tax year, substantially all of our taxable income. In addition, as a BDC, we generally are required to meet a coverage ratio of total assets to total senior securities, which include borrowings and any preferred stock we may issue in the future, of at least 200%. This requirement limits the amount that we may borrow. In January 2008, we received an exemptive order from the SEC to exclude SBA-guaranteed debt securities issued by MSMF and any other wholly owned subsidiaries of ours which operate as SBICs from the asset coverage requirements of the 1940 Act as applicable to us, which, in turn, enables us to fund more investments with debt capital.

        Although we have been able to secure access to additional liquidity, including recent public equity and debt offerings, our expanded $445 million Credit Facility, and the available leverage through the SBIC program, there is no assurance that debt or equity capital will be available to us in the future on favorable terms, or at all.

Recently Issued Accounting Standards

        In February 2013, the Financial Accounting Standards Board issued Accounting Standards Update ("ASU") 2013-04, Liabilities (Topic 405): Obligations Resulting from Joint and Several Liability Arrangements for Which the Total Amount of the Obligation Is Fixed at the Reporting Date ("ASU 2013-04"). ASU 2013-04 provides additional guidance for the recognition, measurement, and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation within the scope of this guidance is fixed at the reporting date. Public companies are required to apply ASU 2013-04 prospectively for interim and annual reporting periods beginning after December 15, 2013.

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        In June 2013, the Financial Accounting Standards Board issued Accounting Standards Update ("ASU") 2013-08, Financial Services—Investment Companies (Topic 946): Amendments to the Scope, Measurement, and Disclosure Requirements ("ASU 2013-08"). ASU 2013-08 amends the criteria that define an investment company, clarifies the measurement guidance and requires certain additional disclosures. Public companies are required to apply ASU 2013-08 prospectively for interim and annual reporting periods beginning after December 15, 2013.

        From time to time, new accounting pronouncements are issued by the FASB or other standards setting bodies that are adopted by us as of the specified effective date. We believe that the impact of recently issued standards that have been issued and any that are not yet effective will not have a material impact on our financial statements upon adoption.

Inflation

        Inflation has not had a significant effect on our results of operations in any of the reporting periods presented herein. However, our portfolio companies have experienced, and may in the future experience, the impacts of inflation on their operating results, including periodic escalations in their costs for raw materials and required energy consumption.

Off-Balance Sheet Arrangements

        We may be a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financial needs of our portfolio companies. These instruments include commitments to extend credit and involve, to varying degrees, elements of liquidity and credit risk in excess of the amount recognized in the balance sheet. At December 31, 2013, we had a total of $95.4 million in outstanding commitments comprised of (i) 12 commitments to fund revolving loans that had not been fully drawn or term loans that had not been funded and (ii) five capital commitments that had not been fully called.

Contractual Obligations

        As of December 31, 2013, the future fixed commitments for cash payments in connection with our SBIC debentures and Notes for each of the next five years and thereafter are as follows:

        As of December 31, 2013, we had $237.0 million in borrowings outstanding under our Credit Facility, and the Credit Facility is currently scheduled to mature in September 2018. The Credit Facility contains two, one year extension options which could extend the maturity to September 2020. See further discussion of the Credit Facility terms in "—Liquidity and Capital Resources—Capital Resources" above.

Related Party Transactions

        Subsequent to the completion of the Formation Transactions through March 31, 2013, the Internal Investment Manager was treated as a wholly owned portfolio company of MSCC and was included as part of our Investment Portfolio. At December 31, 2012, the Internal Investment Manager had a

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receivable of $4.1 million due from MSCC related to operating expenses incurred by the Internal Investment Manager required to support our business. Beginning April 1, 2013, the accounts of the Internal Investment Manager are included as a part of our consolidated financial statements and the Internal Investment Manager is reflected as a consolidated subsidiary, as opposed to being a part of our Investment Portfolio, and any intercompany balances between the Internal Investment Manager and MSCC or any of its other consolidated subsidiaries have been eliminated in consolidation.

        In June 2013, we adopted a deferred compensation plan for the non-employee members of our board of directors, which allows the directors at their option to defer all or a portion of the fees paid for their services as directors and have such deferred fees paid in shares of our common stock within 90 days after the participant's end of service as a director. As of December 31, 2013, $275,000 of directors' fees had been deferred under this plan. These deferred fees represented 9,858 shares of our common shares. These shares will not be issued or included as outstanding on the consolidated statement of changes in net assets until each applicable participant's end of service as a director, but are included in operating expenses and weighted average shares outstanding on our consolidated statement of operations as earned.

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SENIOR SECURITIES

        Information about our senior securities is shown in the following table as of December 31 for the years indicated in the table, unless otherwise noted. Grant Thornton LLP's report on the senior securities table as of December 31, 2013, is an exhibit to the registration statement of which this prospectus supplement is a part.

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BUSINESS

        We are a principal investment firm primarily focused on providing customized debt and equity financing to lower middle market ("LMM") companies and debt capital to middle market ("Middle Market") companies. Our portfolio investments are typically made to support management buyouts, recapitalizations, growth financings, refinancings and acquisitions of companies that operate in diverse industry sectors. We seek to partner with entrepreneurs, business owners and management teams and generally provide "one stop" financing alternatives within our LMM portfolio. We invest primarily in secured debt investments, equity investments, warrants and other securities of LMM companies based in the United States and in secured debt investments of Middle Market companies generally headquartered in the United States.

        Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a portfolio company. Our LMM companies generally have annual revenues between $10 million and $150 million, and our LMM portfolio investments generally range in size from $5 million to $25 million. Our Middle Market investments are made in businesses that are generally larger in size than our LMM portfolio companies, with annual revenues typically between $150 million and $1.5 billion, and our Middle Market investments generally range in size from $3 million to $15 million. Our private loan ("Private Loan") investments are made in businesses that are consistent with the size of companies in our LMM portfolio or our Middle Market portfolio, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. The structure, terms and conditions for these Private Loan investments are typically consistent with the structure, terms and conditions for the loans made in our LMM portfolio or Middle Market portfolio.

        Our other portfolio ("Other Portfolio") investments primarily consist of investments which are not consistent with the typical profiles for our LMM, Middle Market or Private Loan portfolio investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

        Our external asset management business is conducted through our External Investment Manager. We have entered into an agreement through the Internal Investment Manager to provide the External Investment Manager with asset management service support for HMS Income Fund, Inc. ("HMS Income"). Through this agreement, we provide management and other services to the External Investment Manager, as well as access to our employees, infrastructure, business relationships, management expertise and capital raising capabilities. Beginning in the first quarter of 2014, we charge the External Investment Manager a fee for the use of these services. The External Investment Manager earns management fees based on the assets of the funds under management and may earn incentive fees, or a carried interest, based on the performance of the funds managed.

        We seek to fill the current financing gap for LMM businesses, which, historically, have had more limited access to financing from commercial banks and other traditional sources. The underserved nature of the LMM creates the opportunity for us to meet the financing needs of LMM companies while also negotiating favorable transaction terms and equity participations. Our ability to invest across a company's capital structure, from senior secured loans to equity securities, allows us to offer portfolio companies a comprehensive suite of financing options, or a "one stop" financing solution. Providing customized, "one stop" financing solutions has become even more relevant to our LMM portfolio companies in the current investing environment. We generally seek to partner directly with entrepreneurs, management teams and business owners in making our investments. Our LMM portfolio debt investments are generally secured by a first lien on the assets of the portfolio company and

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typically have a term of between five and seven years. We believe that our LMM investment strategy has a lower correlation to the broader debt and equity markets.

        As of December 31, 2013, we had debt and equity investments in 62 LMM portfolio companies with an aggregate fair value of approximately $659.4 million, with a total cost basis of approximately $543.3 million and a weighted average annual effective yield on our LMM debt investments of approximately 14.7%. As of December 31, 2013, approximately 76% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 86% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At December 31, 2013, we had equity ownership in approximately 94% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 33%. As of December 31, 2012, we had debt and equity investments in 56 LMM portfolio companies with an aggregate fair value of approximately $482.9 million, with a total cost basis of approximately $380.5 million, and a weighted average annual effective yield on our LMM debt investments of approximately 14.3%. As of December 31, 2012, approximately 75% of our total LMM portfolio investments at cost were in the form of debt investments and approximately 93% of such debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies. At December 31, 2012, we had equity ownership in approximately 93% of our LMM portfolio companies and the average fully diluted equity ownership in those portfolio companies was approximately 33%. The weighted average annual yields were computed using the effective interest rates for all debt investments at December 31, 2013 and 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments and any debt investments on non-accrual status.

        In addition to our LMM investment strategy, we pursue investments in Middle Market companies. Our Middle Market portfolio investments primarily consist of direct investments in or secondary purchases of interest-bearing debt securities in privately held companies that are generally larger in size than the LMM companies included in our LMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have an expected duration of between three and five years.

        As of December 31, 2013, we had Middle Market portfolio investments in 92 companies collectively totaling approximately $471.5 million in fair value with a total cost basis of approximately $468.3 million. The weighted average EBITDA for the 92 Middle Market portfolio company investments was approximately $79.0 million as of December 31, 2013. As of December 31, 2013, substantially all of our Middle Market portfolio investments were in the form of debt investments and approximately 92% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Middle Market portfolio debt investments was approximately 7.8% as of December 31, 2013. As of December 31, 2012, we had Middle Market portfolio investments in 79 companies, collectively totaling approximately $352.0 million in fair value with a total cost basis of approximately $348.1 million. The weighted average EBITDA for the 79 Middle Market portfolio company investments was approximately $93.5 million as of December 31, 2012. As of December 31, 2012, substantially all of our Middle Market portfolio investments were in the form of debt investments and approximately 91% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Middle Market portfolio debt investments was approximately 8.0% as of December 31, 2012. The weighted average annual yields were computed using the effective interest rates for all debt investments at December 31, 2013 and 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments.

        Our Private Loan portfolio investments primarily consist of investments in interest-bearing debt securities in companies that are consistent with the size of the companies included in our LMM

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portfolio or our Middle Market portfolio. Our Private Loan portfolio debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have a term of between three and seven years.

        As of December 31, 2013, we had Private Loan portfolio investments in 15 companies, collectively totaling approximately $111.5 million in fair value with a total cost basis of approximately $111.3 million. The weighted average EBITDA for the 15 Private Loan portfolio company investments was approximately $18.4 million as of December 31, 2013. As of December 31, 2013, 95% of our Private Loan portfolio investments were in the form of debt investments and 98% of such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Private Loan portfolio debt investments was approximately 11.3% as of December 31, 2013. As of December 31, 2012, we had Private Loan portfolio investments in 9 companies, collectively totaling approximately $65.5 million in fair value with a total cost basis of approximately $64.9 million. The weighted average EBITDA for the 9 Private Loan portfolio company investments was approximately $45.6 million as of December 31, 2012. As of December 31, 2012, approximately 99% of our Private Loan portfolio investments were in the form of debt investments and all such debt investments at cost were secured by first priority liens on portfolio company assets. The weighted average annual effective yield on our Private Loan portfolio debt investments was approximately 14.8% as of December 31, 2012. The weighted average annual yields were computed using the effective interest rates for all debt investments at December 31, 2013 and 2012, including amortization of deferred debt origination fees and accretion of original issue discount but excluding fees payable upon repayment of the debt investments.

        As of December 31, 2013, we had Other Portfolio investments in six companies, collectively totaling approximately $42.8 million in fair value and approximately $40.1 million in cost basis and which comprised 3.3% of our Investment Portfolio at fair value as of December 31, 2013. As of December 31, 2012, we had Other Portfolio investments in three companies, collectively totaling approximately $24.1 million in fair value and approximately $23.6 million in cost basis and which comprised 2.6% of our Investment Portfolio at fair value as of December 31, 2012.

        As discussed above, we hold an investment in the External Investment Manager, a wholly owned subsidiary that is treated as a portfolio investment. As of December 31, 2013, we had no cost basis in this investment and the investment had a fair value of $1.1 million, which comprised 0.1% of our Investment Portfolio.

        During 2013, we began categorizing certain of our portfolio investments that were previously categorized as LMM portfolio investments or Middle Market portfolio investments as Private Loan portfolio investments to provide a separate classification based upon the nature in which such investments are originated. During the year ended December 31, 2013, there were ten portfolio company investment transfers from the LMM and Middle Market portfolio investment categories to the Private Loan portfolio investment category totaling $69.6 million in fair value and $69.0 million in cost on the date of transfer.

        Our portfolio investments are generally made through MSCC and the Funds. MSCC and the Funds share the same investment strategies and criteria, although they are subject to different regulatory regimes (see "Regulation" in the accompanying prospectus). An investor's return in MSCC will depend, in part, on the Funds' investment returns as MSMF and MSC II are both wholly owned subsidiaries of MSCC.

        The level of new portfolio investment activity will fluctuate from period to period based upon our view of the current economic fundamentals, our ability to identify new investment opportunities that meet our investment criteria, and our ability to consummate the identified opportunities. The level of new investment activity, and associated interest and fee income, will directly impact future investment income. In addition, the level of dividends paid by portfolio companies and the portion of our portfolio

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debt investments on non-accrual status will directly impact future investment income. While we intend to grow our portfolio and our investment income over the long-term, our growth and our operating results may be more limited during depressed economic periods. However, we intend to appropriately manage our cost structure and liquidity position based on applicable economic conditions and our investment outlook. The level of realized gains or losses and unrealized appreciation or depreciation will also fluctuate depending upon portfolio activity, economic conditions and the performance of our individual portfolio companies. The changes in realized gains and losses and unrealized appreciation or depreciation could have a material impact on our operating results.

        MSCC and its consolidated subsidiaries are internally managed by the Internal Investment Manager, a wholly owned subsidiary of MSCC, which employs all of the executive officers and other employees of Main Street. Because the Internal Investment Manager is wholly owned by MSCC, Main Street does not pay any external investment advisory fees, but instead incurs the operating costs associated with employing investment and portfolio management professionals through the Internal Investment Manager. We believe that our internally managed structure provides us with a beneficial operating expense structure when compared to other publicly-traded and privately-held investment firms which are externally managed, and our internally managed structure allows us the opportunity to leverage our non-interest operating expenses as we grow our investment portfolio. For the year ended December 31, 2013, the ratio of our total operating expenses, excluding interest expense and excluding the effect of the accelerated vesting of restricted stock (as discussed further above in "Management's Discussion and Analysis of Financial Condition and Results of Operations—Discussion and Analysis of Results of Operations—Comparison of the years ended December 31, 2013 and 2012"), as a percentage of our quarterly average total assets was 1.7% compared to 1.8% for the year ended December 31, 2012. Including the effect of the accelerated vesting of restricted stock, the ratio for the year ended 2013 would have been 1.8%.

        During May 2012, MSCC entered into an investment sub-advisory agreement with HMS Adviser, LP ("HMS Adviser"), which is the investment advisor to HMS Income, a non publicly-traded BDC whose registration statement on Form N-2 was declared effective by the SEC in June 2012, to provide certain investment advisory services to HMS Adviser. In December 2013, after obtaining required relief from the SEC, MSCC assigned the sub-advisory agreement to the External Investment Manager since the fees received from such arrangement could otherwise have negative consequences on MSCC's ability to meet the source-of-income requirement necessary for it to maintain its RIC tax treatment. Under the investment sub-advisory agreement, the External Investment Manager is entitled to 50% of the base management fee and the incentive fees earned by HMS Adviser under its advisory agreement with HMS Income. However, MSCC and the External Investment Manager agreed to waive all such fees from the effective date of HMS Adviser's registration statement on Form N-2 through December 31, 2013. As a result, as of December 31, 2013, neither MSCC nor the External Investment Manager had received any base management fee or incentive fees under the investment sub-advisory agreement and neither is due any unpaid compensation for any base management fee or incentive fees under the investment sub-advisory agreement. Neither MSCC nor the External Investment Manager has waived the External Investment Manager's management or incentive fees after December 31, 2013 and, as a result, the External Investment Manager began accruing such fees on January 1, 2014.

Business Strategies

        Our principal investment objective is to maximize our portfolio's total return by generating current income from our debt investments and realizing capital appreciation from our equity and equity related investments, including warrants, convertible securities and other rights to acquire equity securities in a

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portfolio company. We have adopted the following business strategies to achieve our investment objective:

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Deliver Customized Financing Solutions in the Lower Middle Market.  We offer to our LMM portfolio companies customized debt financing solutions with equity components that are tailored to the facts and circumstances of each situation. We believe our ability to provide a broad range of customized financing solutions to LMM companies sets us apart from other capital providers that focus on providing a limited number of financing solutions. Our ability to invest across a company's capital structure, from senior secured loans to subordinated debt to equity securities, allows us to offer our LMM portfolio companies a comprehensive suite of financing options, or a "one stop" financing solution.



•

Focus on Established Companies.  We generally invest in companies with established market positions, experienced management teams and proven revenue streams. We believe that those companies generally possess better risk adjusted return profiles than newer companies that are building their management teams or are in the early stages of building a revenue base. We also believe that established companies in our targeted size range also generally provide opportunities for capital appreciation.



•

Leverage the Skills and Experience of Our Investment Team.  Our investment team has significant experience in lending to and investing in LMM and Middle Market companies. The members of our investment team have broad investment backgrounds, with prior experience at private investment funds, investment banks and other financial services companies, and currently include five certified public accountants and five Chartered Financial Analyst® (CFA) charter holders. The expertise of our investment team in analyzing, valuing, structuring, negotiating and closing transactions should provide us with competitive advantages by allowing us to consider customized financing solutions and non traditional or complex structures for our portfolio companies. Also, the reputation of our investment team has and should continue to enable us to generate additional revenue in the form of management and incentive fees in connection with us providing advisory services to other investment funds.



•

Invest Across Multiple Companies, Industries, Regions and End Markets.  We seek to maintain a portfolio of investments that is appropriately balanced among various companies, industries, geographic regions and end markets. This portfolio balance is intended to mitigate the potential effects of negative economic events for particular companies, regions, industries and end markets.



•

Capitalize on Strong Transaction Sourcing Network.  Our investment team seeks to leverage its extensive network of referral sources for portfolio company investments. We have developed a reputation in our marketplace as a responsive, efficient and reliable source of financing, which has created a growing stream of proprietary deal flow for us.



•

Benefit from Lower, Fixed, Long Term Cost of Capital.  The SBIC licenses held by the Funds have allowed them to issue SBA guaranteed debentures. SBA guaranteed debentures carry long term fixed interest rates that are generally lower than interest rates on comparable bank loans and other debt. Because lower cost SBA leverage is, and will continue to be, a significant part of our capital base through the Funds, our relative cost of debt capital should be lower than many of our competitors. In addition, the SBIC leverage that we receive through the Funds represents a stable, long term component of our capital structure with proper matching of duration and cost compared to our LMM portfolio investments.

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Investment Criteria

        Our investment team has identified the following investment criteria that it believes are important in evaluating prospective portfolio companies. Our investment team uses these criteria in evaluating investment opportunities. However, not all of these criteria have been, or will be, met in connection with each of our investments.

•

Proven Management Team with Meaningful Equity Stake.  We look for operationally-oriented management with direct industry experience and a successful track record. In addition, we expect the management team of each LMM portfolio company to have meaningful equity ownership in the portfolio company to better align our respective economic interests. We believe management teams with these attributes are more likely to manage the companies in a manner that both protects our debt investment and enhances the value of our equity investment.



•

Established Companies with Positive Cash Flow.  We seek to invest in established companies with sound historical financial performance. We typically focus on LMM companies that have historically generated EBITDA ("Earnings Before Interest, Taxes, Depreciation and Amortization") of $3 million to $20 million and commensurate levels of free cash flow. We also pursue investments in debt securities of Middle Market companies that are generally established companies with sound historical financial performance that are generally larger in size than LMM companies. We generally do not invest in start-up companies or companies with speculative business plans.



•

Defensible Competitive Advantages/Favorable Industry Position.  We primarily focus on companies having competitive advantages in their respective markets and/or operating in industries with barriers to entry, which may help to protect their market position and profitability.



•

Exit Alternatives.  We exit our debt investments primarily through the repayment of our investment from internally generated cash flow of the portfolio company and/or refinancing. In addition, we seek to invest in companies whose business models and expected future cash flows may provide alternate methods of repaying our investment, such as through a strategic acquisition by other industry participants or a recapitalization.

Investment Portfolio

        The Investment Portfolio, as used herein, refers to all of Main Street's LMM portfolio investments, Middle Market portfolio investments, Private Loan portfolio investments, Other Portfolio investments, the investment in the External Investment Manager and, for all periods up to and including March 31, 2013, the investment in the Internal Investment Manager, but excludes all "Marketable securities and idle funds investments", and for all periods after March 31, 2013, the Investment Portfolio also excludes the Internal Investment Manager. For all periods up to and including the period ending March 31, 2013, the Internal Investment Manager was accounted for as a portfolio investment and was not consolidated with MSCC and its consolidated subsidiaries. For all periods after March 31, 2013, the Internal Investment Manager is consolidated with MSCC and its other consolidated subsidiaries. Main Street's LMM portfolio investments principally consist of secured debt, equity warrants and direct equity investments in privately held, LMM companies based in the United States. Main Street's Middle Market portfolio investments primarily consist of direct investments in or secondary purchases of interest-bearing debt securities in companies based in the United States that are generally larger in size than the companies included in Main Street's LMM portfolio. Main Street's Private Loan portfolio investments primarily consist of investments in interest- bearing debt securities in companies that are consistent with the size of companies in our LMM portfolio or our Middle Market portfolio, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. Main Street's Other Portfolio investments primarily consist of investments which are not consistent with the typical profiles for our LMM, Middle Market and Private Loan portfolio

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investments, including investments which may be managed by third parties. In our Other Portfolio, we may incur indirect fees and expenses in connection with investments managed by third parties, such as investments in other investment companies or private funds.

Debt Investments

        Historically, we have made LMM debt investments principally in the form of single tranche debt. Single tranche debt financing involves issuing one debt security that blends the risk and return profiles of both first lien secured and subordinated debt. We believe that single tranche debt is more appropriate for many LMM companies given their size in order to reduce structural complexity and potential conflicts among creditors.

        Our LMM debt investments generally have terms of three to seven years, with limited required amortization prior to maturity, and provide for monthly or quarterly payment of interest at fixed interest rates generally between 12% and 14% per annum, payable currently in cash. In some instances, we have provided floating interest rates for a portion of a single tranche debt security. In addition, certain LMM debt investments may have a form of interest that is not paid currently but is accrued and added to the loan balance and paid at maturity. We refer to this as payment-in-kind, or PIK, interest. We typically structure our LMM debt investments with the maximum seniority and collateral that we can reasonably obtain while seeking to achieve our total return target. In most cases, our LMM debt investment will be collateralized by a first priority lien on substantially all the assets of the portfolio company. As of December 31, 2013, approximately 86% of our LMM debt investments at cost were secured by first priority liens on the assets of our LMM portfolio companies.

        In addition to seeking a senior lien position in the capital structure of our LMM portfolio companies, we seek to limit the downside potential of our LMM investments by negotiating covenants that are designed to protect our LMM investments while affording our portfolio companies as much flexibility in managing their businesses as is reasonable. Such restrictions may include affirmative and negative covenants, default penalties, lien protection, change of control or change of management provisions, key-man life insurance, guarantees, equity pledges, personal guaranties, where appropriate, and put rights. In addition, we typically seek board representation or observation rights in all of our LMM portfolio companies.

        While we will continue to focus our LMM investments primarily on single tranche debt investments, we also anticipate structuring some of our debt investments as mezzanine loans. We anticipate that these mezzanine loans will be primarily junior secured or unsecured, subordinated loans that provide for relatively high fixed interest rates payable currently in cash that will provide us with significant interest income plus the additional opportunity for income and gains through PIK interest and equity warrants and other similar equity instruments issued in conjunction with these mezzanine loans. These loans typically will have interest-only payments in the early years, with amortization of principal deferred to the later years of the mezzanine loan term. Typically, our mezzanine loans will have maturities of three to five years. We will generally target fixed interest rates of 12% to 14%, payable currently in cash for our mezzanine loan investments with higher targeted total returns from equity warrants or PIK interest.

        We also pursue debt investments in Middle Market companies. Our Middle Market portfolio investments primarily consist of direct investments or secondary purchases of interest-bearing debt securities in companies based in the United States that are generally larger in size than the companies included in our LMM portfolio. Our Middle Market portfolio debt investments are generally secured by either a first or second priority lien on the assets of the company and typically have a term of between three and five years. The debt investments in our Middle Market portfolio have rights and protections that are similar to those in our LMM debt investments, which may include affirmative and negative covenants, default penalties, lien protection, change of control provisions, guarantees, and

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equity pledges. The Middle Market debt investments generally have floating interest rates at LIBOR plus a margin, and are typically subject to LIBOR floors. As of December 31, 2013, substantially all of our Middle Market portfolio investments were in the form of debt investments, with approximately 99% of these investments at cost secured by portfolio company assets and approximately 92% of such debt investments at cost secured by first priority liens.

        Our Private Loan portfolio investments primarily consist of investments in interest-bearing debt securities in companies that are consistent with the size of companies in our LMM portfolio or our Middle Market portfolio, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. Our Private Loan portfolio debt investments are generally secured by either a first or second priority lien and typically have a term of between three and seven years. As of December 31, 2013, approximately 95% of Main Street's Private Loan portfolio investments were in the form of debt investments and approximately 98% of such debt investments at cost were secured by first priority liens on portfolio company assets.

Warrants

        In connection with a portion of our LMM debt investments, we have historically received equity warrants to establish or increase our equity interest in the LMM portfolio company. Warrants we receive in connection with a LMM debt investment typically require only a nominal cost to exercise, and thus, as a LMM portfolio company appreciates in value, we may achieve additional investment return from this equity interest. We typically structure the warrants to provide provisions protecting our rights as a minority-interest holder, as well as secured or unsecured put rights, or rights to sell such securities back to the LMM portfolio company, upon the occurrence of specified events. In certain cases, we also may obtain registration rights in connection with these equity interests, which may include demand and "piggyback" registration rights.

Direct Equity Investments

        We also will seek to make direct equity investments in situations where it is appropriate to align our interests with key management and stockholders of our LMM portfolio companies, and to allow for participation in the appreciation in the equity values of our LMM portfolio companies. We usually make our direct equity investments in connection with debt investments. In addition, we may have both equity warrants and direct equity positions in some of our LMM portfolio companies. We seek to maintain fully diluted equity positions in our LMM portfolio companies of 5% to 50%, and may have controlling equity interests in some instances. We have a value orientation toward our direct equity investments and have traditionally been able to purchase our equity investments at reasonable valuations.

Investment Process

        Our investment committee is responsible for all aspects of our LMM investment process. The current members of our investment committee are Vincent D. Foster, our Chairman, President and Chief Executive Officer, Dwayne L. Hyzak, our Chief Financial Officer and Senior Managing Director, Curtis L. Hartman, our Chief Credit Officer and Senior Managing Director and David Magdol, our Chief Investment Officer and Senior Managing Director.

        Our credit committee is responsible for all aspects of our Middle Market portfolio investment process. The current members of our credit committee are Messrs. Foster, Hartman, and Rodger A. Stout, our Executive Vice President.

        Investment process responsibility for each Private Loan portfolio investment is delegated to either the investment committee or the credit committee based upon the nature of the investment and the manner in which it was originated. Similarly, the investment processes for each Private Loan portfolio

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investment, from origination to close and to eventual exit, will follow the processes for our LMM portfolio investments or our Middle Market portfolio investments as outlined below, or a combination thereof.

        Our investment strategy involves a "team" approach, whereby potential transactions are screened by several members of our investment team before being presented to the investment committee or the credit committee, as applicable. Our investment committee and credit committee each meet on an as needed basis depending on transaction volume. We generally categorize our investment process into seven distinct stages:

Deal Generation/Origination

        Deal generation and origination is maximized through long-standing and extensive relationships with industry contacts, brokers, commercial and investment bankers, entrepreneurs, service providers such as lawyers, financial advisors, accountants and current and former portfolio companies and investors. Our investment team has focused its deal generation and origination efforts on LMM and Middle Market companies, and we have developed a reputation as a knowledgeable, reliable and active source of capital and assistance in these markets.

Screening

        During the screening process, if a transaction initially meets our investment criteria, we will perform preliminary due diligence, taking into consideration some or all of the following information:

•

a comprehensive financial model based on quantitative analysis of historical financial performance, projections and pro forma adjustments to determine the estimated internal rate of return;



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a brief industry and market analysis;



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direct industry expertise imported from other portfolio companies or investors;



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preliminary qualitative analysis of the management team's competencies and backgrounds;



•

potential investment structures and pricing terms; and



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regulatory compliance.

        Upon successful screening of a proposed LMM transaction, the investment team makes a recommendation to our investment committee. If our investment committee concurs with moving forward on the proposed LMM transaction, we typically issue a non-binding term sheet to the company. For Middle Market portfolio investments, the initial term sheet is typically issued by the borrower, through the syndicating bank, and is screened by the investment team which makes a recommendation to our credit committee.

Term Sheet

        For proposed LMM transactions, the non-binding term sheet will include the key economic terms based upon our analysis performed during the screening process as well as a proposed timeline and our qualitative expectation for the transaction. While the term sheet for LMM investments is non-binding, we typically receive an expense deposit in order to move the transaction to the due diligence phase. Upon execution of a term sheet, we begin our formal due diligence process.

        For proposed Middle Market transactions, the initial term sheet will include key economic terms and other conditions proposed by the borrower and its representatives and the proposed timeline for the investment, which are reviewed by our investment team to determine if such terms and conditions are in agreement with Main Street's investment objectives.

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Due Diligence

        Due diligence on a proposed LMM investment is performed by a minimum of two of our investment professionals, whom we refer to collectively as the investment team, and certain external resources, who together conduct due diligence to understand the relationships among the prospective portfolio company's business plan, operations and financial performance. Our LMM due diligence review includes some or all of the following:

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site visits with management and key personnel;



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detailed review of historical and projected financial statements;



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operational reviews and analysis;



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interviews with customers and suppliers;



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detailed evaluation of company management, including background checks;



•

review of material contracts;



•

in-depth industry, market, and strategy analysis;



•

regulatory compliance analysis; and



•

review by legal, environmental or other consultants, if applicable.

        Due diligence on a proposed Middle Market investment is generally performed on materials and information obtained from certain external resources and assessed internally by a minimum of two of our investment professionals, who work to understand the relationships among the prospective portfolio company's business plan, operations and financial performance using the accumulated due diligence information. Our Middle Market due diligence review includes some or all of the following:

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detailed review of historical and projected financial statements;



•

in-depth industry, market, operational and strategy analysis;



•

regulatory compliance analysis; and



•

detailed review of the company's management team and their capabilities.

        During the due diligence process, significant attention is given to sensitivity analyses and how the company might be expected to perform given downside, base-case and upside scenarios. In certain cases, we may decide not to make an investment based on the results of the diligence process.

Document and Close

        Upon completion of a satisfactory due diligence review of a proposed LMM portfolio investment, the investment team presents the findings and a recommendation to our investment committee. The presentation contains information which can include, but is not limited to, the following:

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company history and overview;



•

transaction overview, history and rationale, including an analysis of transaction strengths and risks;



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analysis of key customers and suppliers and key contracts;



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a working capital analysis;



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an analysis of the company's business strategy;



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a management and key equity investor background check and assessment;

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•

third-party accounting, legal, environmental or other due diligence findings;



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investment structure and expected returns;



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anticipated sources of repayment and potential exit strategies;



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pro forma capitalization and ownership;



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an analysis of historical financial results and key financial ratios;



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sensitivities to management's financial projections;



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regulatory compliance analysis findings; and



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detailed reconciliations of historical to pro forma results.

        Upon completion of a satisfactory due diligence review of a proposed Middle Market portfolio investment, the investment team presents the findings and a recommendation to our credit committee. The presentation contains information which can include, but is not limited to, the following:

•

company history and overview;



•

transaction overview, history and rationale, including an analysis of transaction strengths and risks;



•

analysis of key customers and suppliers;



•

an analysis of the company's business strategy;



•

investment structure and expected returns;



•

anticipated sources of repayment and potential exit strategies;



•

pro forma capitalization and ownership;



•

regulatory compliance analysis findings; and



•

an analysis of historical financial results and key financial ratios.

        If any adjustments to the transaction terms or structures are proposed by the investment committee or credit committee, as applicable, such changes are made and applicable analyses are updated prior to approval of the transaction. Approval for the transaction must be made by the affirmative vote from a majority of the members of the investment committee or credit committee, as applicable, with the committee member managing the transaction, if any, abstaining from the vote. Upon receipt of transaction approval, we will re- confirm regulatory compliance, process and finalize all required legal documents, and fund the investment.

Post-Investment

        We continuously monitor the status and progress of the portfolio companies. We generally offer managerial assistance to our portfolio companies, giving them access to our investment experience, direct industry expertise and contacts. The same investment team that was involved in the investment process will continue its involvement in the portfolio company post-investment. This provides for continuity of knowledge and allows the investment team to maintain a strong business relationship with key management of our portfolio companies for post-investment assistance and monitoring purposes. As part of the monitoring process of LMM portfolio investments, the investment team will analyze monthly and quarterly financial statements versus the previous periods and year, review financial projections, meet and discuss issues or opportunities with management, attend board meetings and review all compliance certificates and covenants. While we maintain limited involvement in the ordinary course operations of our LMM portfolio companies, we maintain a higher level of involvement in

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non-ordinary course financing or strategic activities and any non-performing scenarios. We also monitor the performance of our Middle Market portfolio investments; however, due to the larger size and higher sophistication level of these Middle Market companies in comparison to our LMM portfolio companies, it is not necessary or practical to have as much direct management interface.

        We utilize an internally developed investment rating system to rate the performance of each LMM portfolio company and to monitor our expected level of returns on each of our LMM investments in relation to our expectations for the portfolio company. The investment rating system takes into consideration various factors, including, but not limited to, each investment's expected level of returns and the collectability of our debt investments, comparisons to competitors and other industry participants and the portfolio company's future outlook.

•

Investment Rating 1 represents a portfolio company that is performing in a manner which significantly exceeds expectations;



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Investment Rating 2 represents a portfolio company that, in general, is performing above expectations;



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Investment Rating 3 represents a portfolio company that is generally performing in accordance with expectations;



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Investment Rating 4 represents a portfolio company that is underperforming expectations. Investments with such a rating require increased Main Street monitoring and scrutiny; and



•

Investment Rating 5 represents a portfolio company that is significantly underperforming. Investments with such a rating require heightened levels of monitoring and scrutiny by us and involve the recognition of significant unrealized depreciation on such investment.

        All new LMM portfolio investments receive an initial 3 rating.

        The following table shows the distribution of our LMM portfolio investments on the 1 to 5 investment rating scale at fair value as of December 31, 2013 and 2012:

        Based upon our investment rating system, the weighted average rating of our LMM portfolio as of December 31, 2013 and 2012 was approximately 2.2 and 2.1, respectively.

        For the total Investment Portfolio, as of December 31, 2013, we had two investments with positive fair value on non-accrual status which comprised approximately 2.3% of the total Investment Portfolio at fair value and 4.7% of the total Investment Portfolio at cost and no fully impaired investments. For the total Investment Portfolio, as of December 31, 2012, we had no investments with positive fair value on non-accrual status and one fully impaired investment which comprised approximately 0.2% of the total Investment Portfolio at cost on non-accrual status, excluding the investment in the affiliated Internal Investment Manager.

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Exit Strategies/Refinancing

        While we generally exit most investments through the refinancing or repayment of our debt and redemption of our equity positions, we typically assist our LMM portfolio companies in developing and planning exit opportunities, including any sale or merger of our portfolio companies. We may also assist in the structure, timing, execution and transition of the exit strategy. The refinancing or repayment of Middle Market debt investments typically does not require our assistance due to the additional resources available to these larger, Middle Market companies.

Determination of Net Asset Value and Portfolio Valuation Process

        We determine the net asset value per share of our common stock on a quarterly basis. The net asset value per share is equal to our total assets minus liabilities and any noncontrolling interests outstanding divided by the total number of shares of common stock outstanding.

        We are required to report our investments at fair value. As a result, the most significant determination inherent in the preparation of our consolidated financial statements is the valuation of our Investment Portfolio and the related amounts of unrealized appreciation and depreciation. As of December 31, 2013 and 2012, approximately 95% and 89%, respectively, of our total assets at each date represented investments in our Investment Portfolio valued at fair value. We follow the provisions of the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("Codification" or "ASC") 820, Fair Value Measurements and Disclosures ("ASC 820"). ASC 820 defines fair value, establishes a framework for measuring fair value, establishes a fair value hierarchy based on the quality of inputs used to measure fair value, and enhances disclosure requirements for fair value measurements.

        Our business strategy calls for us to invest primarily in illiquid debt and equity securities issued by private, LMM companies and debt securities issued by Middle Market companies that are generally larger in size than the LMM companies. We also categorize some of our investments in LMM and Middle Market companies as Private Loan portfolio investments, which are typically debt securities issued by companies that are consistent in size with either our LMM or Middle Market companies, but are investments which have been originated through strategic relationships with other investment funds on a collaborative basis. Our portfolio also includes Other Portfolio investments which primarily consist of investments which are not consistent with the typical profiles for our LMM portfolio investments, Middle Market portfolio investments or Private Loan portfolio investments, including investments which may be managed by third parties. All of these portfolio investments may be subject to restrictions on resale.

        LMM investments and Other Portfolio investments generally have no established trading market while Middle Market securities generally have established markets that are not active. Private Loan investments may include investments which have no established trading market or have established markets that are not active. We determine in good faith the fair value of our Investment Portfolio pursuant to a valuation policy in accordance with ASC 820 and a valuation process approved by our Board of Directors and in accordance with the 1940 Act. Our valuation policy and process is intended to provide a consistent basis for determining the fair value of our Investment Portfolio.

        For LMM investments, we generally review external events, including private mergers, sales and acquisitions involving comparable companies, and include these events in the valuation process. For Middle Market portfolio investments, we primarily use observable inputs such as quoted prices in the valuation process. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we generally use a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

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        For valuation purposes, "control" LMM portfolio investments are composed of debt and equity securities in companies for which we have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Market quotations are generally not readily available for our control LMM portfolio investments. As a result, for control LMM portfolio investments, we generally determine the fair value using a combination of market and income approaches. Under the market approach, we will typically use the enterprise value methodology to determine the fair value of these investments. The enterprise value is the fair value at which an enterprise could be sold in a transaction between two willing parties, other than through a forced or liquidation sale. Typically, private companies are bought and sold based on multiples of earnings before interest, taxes, depreciation and amortization, or EBITDA, cash flows, net income, revenues, or in limited cases, book value. There is no single methodology for estimating enterprise value. For any one portfolio company, enterprise value is generally described as a range of values from which a single estimate of enterprise value is derived. In estimating the enterprise value of a portfolio company, we analyze various factors, including the portfolio company's historical and projected financial results. We allocate the enterprise value to investments in order of the legal priority of the various components of the portfolio company's capital structure. We will also use the income approach to determine the fair value of these securities, based on projections of the discounted future free cash flows that the portfolio company or the debt security will likely generate, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments.. The valuation approaches for our control LMM portfolio investments estimate the value of the investment if we were to sell, or exit, the investment. In addition, these valuation approaches consider the value associated with our ability to control the capital structure of the portfolio company, as well as the timing of a potential exit.

        For valuation purposes, "non-control" LMM portfolio investments are generally composed of debt and equity securities in companies for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Market quotations are generally not readily available for non-control LMM portfolio investments. For our non-control LMM investments, we use a combination of the market and income approaches to value our equity investments and the income approach to value our debt investments similar to the approaches used for our control LMM portfolio investments, and which includes using a yield-to-maturity approach that analyzes the discounted cash flows of interest and principal for the debt security, as set forth in the associated loan agreements, as well as the financial position and credit risk of each of these portfolio investments. Our estimate of the expected repayment date of a LMM debt security is generally the legal maturity date of the instrument, as we generally intend to hold our LMM loans and debt securities to maturity. The yield-to-maturity analysis considers changes in leverage levels, credit quality, portfolio company performance and other factors. We will use the value determined by the yield-to-maturity analysis as the fair value for that security; however, because of our general intent to hold our loans to maturity, the fair value will not exceed the principal amount of the LMM debt security. A change in the assumptions that we use to estimate the fair value of our LMM debt securities using the yield-to-maturity analysis could have a material impact on the determination of fair value. If there is deterioration in credit quality or if a LMM debt security is in workout status, we may consider other factors in determining the fair value of the LMM debt security, including the value attributable to the debt security from the enterprise value of the portfolio company or the proceeds that would most likely be received in a liquidation analysis.

        Pursuant to our internal valuation process and the requirements under the 1940 Act, we perform valuation procedures on our investments in each LMM portfolio company once a quarter. In addition to our internal valuation process, in arriving at estimates of fair value for our investments in LMM portfolio companies, we, among other things, consult with a nationally recognized independent advisor. The nationally recognized independent advisor is generally consulted relative to our investments in each

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LMM portfolio company at least once in every calendar year, and for our investments in new LMM portfolio companies, at least once in the twelve-month period subsequent to the initial investment. In certain instances, we may determine that it is not cost-effective, and as a result is not in our stockholders' best interest, to consult with the nationally recognized independent advisor on our investments in one or more LMM portfolio companies. Such instances include, but are not limited to, situations where the fair value of our investment in a LMM portfolio company is determined to be insignificant relative to the total investment portfolio. We consulted with our independent advisor in arriving at our determination of fair value on our investments in a total of 50 LMM portfolio companies for the year ended December 31, 2013, representing approximately 76% of the total LMM portfolio at fair value as of December 31, 2013 and on a total of 47 LMM portfolio companies for the year ended December 31, 2012, representing approximately 80% of the total LMM portfolio and investment in the affiliated Internal Investment Manager at fair value as of December 31, 2012. Excluding our investments in new LMM portfolio companies which have not been in our Investment Portfolio for at least twelve months subsequent to the initial investment as of December 31, 2013 and 2012, as applicable, the percentage of the LMM portfolio reviewed was over 99% of total LMM portfolio at fair value as of December 31, 2013 and 99% of total LMM portfolio and investment in the affiliated Internal Investment Manager at fair value as of December 31, 2012.

        Our Middle Market portfolio investments primarily consist of direct investments in or secondary purchases of interest-bearing debt securities in companies that are generally larger in size than the LMM companies included in our Investment Portfolio. For valuation purposes, all of our Middle Market portfolio investments are non-control investments for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. We primarily use observable inputs to determine the fair value of these investments through obtaining third party quotes or independent pricing, to the extent such sufficient observable inputs are available, to determine fair value. For Middle Market portfolio investments for which sufficient observable inputs are not available to determine fair value, we use a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        Our Private Loan portfolio investments primarily consist of direct investments in or secondary purchases of interest-bearing debt securities in companies that are consistent with the size of companies included in our LMM portfolio or our Middle Market portfolio. For valuation purposes, all of our Private Loan portfolio investments are non-control investments for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. As sufficient observable inputs to determine the fair value of these Private Loan portfolio investments through obtaining third party pricing or other independent pricing are not generally available, we generally use a combination of observable inputs through obtaining third party quotes or other independent pricing and an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        For valuation purposes, all of our Other Portfolio investments are non-control investments for which we do not have a controlling interest in the portfolio company or the ability to nominate a majority of the portfolio company's board of directors. Our Other Portfolio investments comprised 3.3% and 2.6%, respectively, of our Investment Portfolio at fair value as of December 31, 2013 and 2012. Similar to the LMM investment portfolio, market quotations for Other Portfolio equity investments are generally not readily available. For our Other Portfolio equity investments, we determine the fair value based on the fair value of the portfolio company as determined by independent third parties and based on our proportional ownership in the portfolio company, as well as the financial position and assessed risk of each of these portfolio investments. For Other Portfolio debt investments with observable inputs, we determine the fair value of these investments through obtaining

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third party quotes or other independent pricing, to the extent such sufficient observable inputs are available, to determine fair value. To the extent observable inputs are not available, we value these Other Portfolio debt investments through an approach similar to the income approach using a yield-to-maturity model used to value our LMM portfolio debt investments.

        For valuation purposes, our investment in the External Investment Manager is a control investment for which we have a controlling interest in the portfolio company and the ability to nominate a majority of the portfolio company's board of directors. Market quotations are not readily available for this investment, and as a result, we determine the fair value of the External Investment Manager using the enterprise value methodology under the market approach. In estimating the enterprise value, we analyze various factors, including the entity's historical and projected financial results, as well as its size, marketability and performance relative to the population of market multiples. This valuation approach estimates the value of the investment if we were to sell, or exit, the investment. In addition, we consider the value associated with our ability to control the capital structure of the company, as well as the timing of a potential exit.

        Due to the inherent uncertainty in the valuation process, our determination of fair value for our Investment Portfolio may differ materially from the values that would have been determined had a ready market for the securities existed. In addition, changes in the market environment, portfolio company performance and other events that may occur over the lives of the investments may cause the gains or losses ultimately realized on these investments to be materially different than the valuations currently assigned. We determine the fair value of each individual investment and record changes in fair value as unrealized appreciation or depreciation.

        As described below, we undertake a multi-step valuation process each quarter in connection with determining the fair value of our investments, with our Board of Directors having final responsibility for overseeing, reviewing and approving, in good faith, our determination of the fair value of each individual investment.

•

Our quarterly valuation process begins with each LMM and Private Loan portfolio company investment being initially valued by the investment team responsible for monitoring the portfolio investment;



•

The fair value determination for our Middle Market and Other Portfolio debt and equity investments and our investment in the External Investment Manager consists of unobservable and observable inputs which are initially reviewed by the investment professionals responsible for monitoring the portfolio investment;



•

Preliminary valuation conclusions are then reviewed by and discussed with senior management, and the investment team considers and assesses, as appropriate, any changes that may be required to the preliminary valuations to address any comments provided by senior management;



•

As described above, a nationally recognized independent advisor performs certain mutually agreed limited procedures that we and the Board of Directors have identified and asked them to perform on a selection of management's LMM portfolio company valuation conclusions;



•

The Audit Committee of our Board of Directors reviews management's valuations, and the investment team and senior management consider and assess, as appropriate, any changes that may be required to management's valuations to address any comments provided by the Audit Committee; and



•

The Board of Directors assesses the valuations and ultimately approves the fair value of each investment in our portfolio in good faith.

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        Determination of fair value involves subjective judgments and estimates. The notes to our financial statements will refer to the uncertainty with respect to the possible effect of such valuations, and any change in such valuations, on our financial statements.

Competition

        We compete for investments with a number of investment funds (including private equity funds, mezzanine funds, BDCs, and SBICs), as well as traditional financial services companies such as commercial banks and other sources of financing. Many of the entities that compete with us have greater financial and managerial resources. We believe we are able to be competitive with these entities primarily on the basis of our focus toward the underserved LMM, the experience and contacts of our management team, our responsive and efficient investment analysis and decision-making processes, our comprehensive suite of customized financing solutions and the investment terms we offer.

        We believe that some of our competitors make senior secured loans, junior secured loans and subordinated debt investments with interest rates and returns that are comparable to or lower than the rates and returns that we target. Therefore, we do not seek to compete primarily on the interest rates and returns that we offer to potential portfolio companies. For additional information concerning the competitive risks we face, see "Risk Factors—Risks Related to Our Business and Structure—We may face increasing competition for investment opportunities" in the accompanying prospectus.

Employees

        As of December 31, 2013, we had 37 employees, each of whom was employed by the Internal Investment Manager. These employees include investment and portfolio management professionals, operations professionals and administrative staff. As necessary, we will hire additional investment professionals and administrative personnel. All of our employees are located in our Houston, Texas office.

Properties

        We do not own any real estate or other physical properties materially important to our operations. Currently, we lease office space in Houston, Texas for our corporate headquarters.

Legal Proceedings

        We may, from time to time, be involved in litigation arising out of our operations in the normal course of business or otherwise. Furthermore, third parties may seek to impose liability on us in connection with the activities of our portfolio companies. While the outcome of any current legal proceedings cannot at this time be predicted with certainty, we do not expect any current matters will materially affect our financial condition or results of operations; however, there can be no assurance whether any pending legal proceedings will have a material adverse effect on our financial condition or results of operations in any future reporting period.

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MANAGEMENT

        Our business and affairs are managed under the direction of our Board of Directors. Our Board of Directors appoints our officers, who serve at the discretion of the Board of Directors. The responsibilities of the Board of Directors include, among other things, the oversight of our investment activities, the quarterly valuation of our assets, oversight of our financing arrangements and corporate governance activities. The Board of Directors has an Audit Committee, Compensation Committee, and Nominating and Corporate Governance Committee, and may establish additional committees from time to time as necessary.

Board of Directors and Executive Officers

        Our Board of Directors consists of six members, five of whom are classified under applicable NYSE listing standards as "independent" directors and under Section 2(a)(19) of the 1940 Act as "non-interested" persons. Pursuant to our articles of incorporation, each member of our Board of Directors serves a one year term, with each current director serving until the 2014 Annual Meeting of Stockholders and until his respective successor is duly qualified and elected. Our articles of incorporation give our Board of Directors sole authority to appoint directors to fill vacancies that are created either through an increase in the number of directors or due to the resignation, removal or death of any director.

Directors

        Information regarding our current Board of Directors is set forth below as of March 12, 2014. We have divided the directors into two groups—independent directors and interested directors. Interested directors are "interested persons" of MSCC as defined in Section 2(a)(19) of the 1940 Act. The address for each director is c/o Main Street Capital Corporation, 1300 Post Oak Boulevard, Suite 800, Houston, Texas 77056.

Independent Directors

Interested Directors

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Executive Officers

        The following persons serve as our executive officers or significant employees in the following capacities (information as of March 12, 2014):