Registration No. 333-103392
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                 --------------


                               AMENDMENT NO. 2 TO
                                    FORM S-3
             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933


                                 --------------

                          UNISOURCE ENERGY CORPORATION
             (Exact name of registrant as specified in its charter)


            ARIZONA                                      86-0786732
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
 incorporation or organization)


                             ONE SOUTH CHURCH AVENUE
                                   SUITE 1820
                             TUCSON, ARIZONA, 85701
                                 (520) 571-4000
    (Address, including zip code, and telephone number, including area code,
                  of registrant's principal executive offices)



            Kevin P. Larson                        John T. Hood, Esq.
 Vice President, Chief Financial Officer        Thelen Reid & Priest LLP
              and Treasurer                        875 Third Avenue
      UniSource Energy Corporation              New York, New York 10022
   One South Church Avenue, Suite 1820               (212) 603-2000
          Tucson, Arizona 85701
             (520) 571-4000


       (Names and addresses, including zip codes, and telephone numbers,
                  including area codes, of agents for service)

                                 --------------






                    Subject to Completion, Dated May 9, 2003


P R O S P E C T U S
-------------------



                                4,000,000 SHARES
                          UNISOURCE ENERGY CORPORATION

                                  COMMON STOCK
                                WITHOUT PAR VALUE
                                 --------------


     By this prospectus, UniSource Energy may offer from time to time up to
4,000,000 shares of its common stock and the attached preferred share purchase
rights. In this prospectus, we refer to the common stock and the attached
preferred share purchase rights together as the "Shares."

     UniSource Energy's common stock is listed on the New York Stock Exchange
and the Pacific Exchange. The ticker symbol is: UNS.

     One or more supplements to this prospectus will indicate the amount and
terms of each offering of Shares, including the offering price. UniSource Energy
may sell its Shares to or through underwriters, dealers or agents or directly to
one or more purchasers.

          You should read this prospectus and the applicable prospectus
                     supplement carefully before you invest.

                                 --------------

     NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE
ADEQUACY OR ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.



                 THE DATE OF THIS PROSPECTUS IS ________, 2003.


The information in this prospectus is not complete and may be changed. We may
not sell these securities until the registration statement filed with the
Securities and Exchange Commission is effective. This prospectus is not an offer
to sell these securities and it is not soliciting an offer to buy these
securities in any state where the offer or sale is not permitted.





                                TABLE OF CONTENTS

                                                                            Page
                                                                            ----

IMPORTANT INFORMATION ABOUT THIS PROSPECTUS....................................1

UNISOURCE ENERGY...............................................................2

USE OF PROCEEDS................................................................3

DESCRIPTION OF CAPITAL STOCK...................................................4

PLAN OF DISTRIBUTION...........................................................8

WHERE YOU CAN FIND MORE INFORMATION............................................9

FORWARD-LOOKING STATEMENTS....................................................11

EXPERTS.......................................................................12

LEGAL MATTERS.................................................................12



                   IMPORTANT INFORMATION ABOUT THIS PROSPECTUS

     This prospectus is part of a "shelf" registration statement that we filed
with the United States Securities and Exchange Commission (SEC). We may sell the
Shares described in this prospectus from time to time in one or more offerings.
This prospectus only provides you with a general description of the Shares. Each
time we offer Shares, we will provide a supplement to this prospectus that
contains specific information about the terms of such offering of the Shares.
The supplement may also add, update or change information contained in this
prospectus.

     In addition to the information contained in this prospectus and the
applicable supplement, this prospectus incorporates by reference important
business and financial information about UniSource Energy that is not included
in or delivered with this prospectus. See "WHERE YOU CAN FIND MORE INFORMATION."

     You should rely only on the information contained or incorporated by
reference in this prospectus and the applicable supplement. We have not
authorized any other person to provide you with different information. You
should not assume that the information contained or incorporated in this
prospectus as of any time after the date of this prospectus or, if later, the
date of an incorporated document, is accurate because our business, financial
condition or results of operations may have changed since that date.

     We are not making an offer to sell any securities in any jurisdiction where
an offer or sale is not permitted.





                                UNISOURCE ENERGY

     UniSource Energy is a holding company that owns the outstanding common
stock of Tucson Electric Power Company (TEP), Millennium Energy Holdings, Inc.
(Millennium) and UniSource Energy Development Company (UED). UniSource Energy is
an Arizona corporation and an exempt holding company pursuant to Section 3(a)(1)
of the Public Utility Holding Company Act of 1935, as amended, and Rule 2
thereunder. References in this prospectus to "we" and "our" are to UniSource
Energy.

TEP

     TEP is our principal subsidiary and represents most of our assets. TEP is a
vertically integrated utility that provides regulated electric service to over
355,000 retail customers in its service territory. This service territory
consists of a 1,155 square mile area of Southeastern Arizona with a population
of approximately 891,000 in the greater Tucson metropolitan area in Pima County,
as well as parts of Cochise County. TEP holds a franchise to provide electric
distribution service to customers in the City of Tucson. This franchise expires
in 2026. TEP also sells electricity to other utilities and power marketing
entities in the western U.S. At December 31, 2002, TEP owned or leased 2,002 MW
of net generating capability.

     The Federal Energy Regulatory Commission (FERC) and the Arizona Corporation
Commission (ACC) regulate portions of TEP's utility accounting practices and
electricity rates. The FERC regulates the terms and prices of TEP's sales to
other utilities and resellers. The ACC has authority over certain rates charged
to retail customers, the issuance of securities, and transactions with
affiliated parties.

MILLENNIUM

     Millennium's assets comprised approximately 6% of the consolidated assets
of UniSource Energy at December 31, 2001. Through its affiliates, Millennium
holds investments in the following subsidiaries including:

     o    Global Solar Energy, Inc., a developer and manufacturer of flexible
          thin-film photovoltaic cells. Target markets for its products include
          military, space and commercial applications.

     o    Infinite Power Solutions, Inc., a developer of thin-film batteries.

     o    MicroSat Systems, Inc., a developer of small-scale satellites,
          focusing on research and development activities related to government
          contracts.

UED

     UED, established in 2001, is the developer of the expansion project at the
Springerville Generating Station.

EFFECT OF HOLDING COMPANY STRUCTURE

     Since UniSource Energy is a holding company, substantially all of the
assets shown on UniSource Energy's consolidated balance sheet are held by its
subsidiaries. Accordingly, UniSource Energy's earnings and cash flow and its
ability to meet its obligations are dependent upon the earnings and cash flows
of such subsidiaries and the distribution or other payment of such earnings to
UniSource Energy. The subsidiaries are separate and distinct legal entities and
have no obligation to make any such distribution or other payment to UniSource
Energy and may do so only after they satisfy their debt obligations and any


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preferred stock requirements, and comply with any statutory or contractual
limitations.

     Any shares of UniSource Energy common stock which may be offered by this
prospectus are, by definition, junior to claims of UniSource Energy's creditors
including, but not limited to, holders of debt securities that may be issued or
guaranteed by UniSource Energy and, as discussed above, to the claims of
creditors of UniSource Energy's subsidiaries. In addition, our articles of
incorporation permit us to issue preferred stock. Before we can pay dividends on
our common stock, we must satisfy our current debt obligations and any preferred
stock requirements, and comply with any statutory or contractual limitations.

     UniSource Energy's Board of Directors periodically reviews our dividend
level, taking into consideration a number of factors including our results of
operations and financial condition, general economic and competitive conditions
and the earnings and cash flows of our subsidiary companies, TEP, Millennium and
UED. As discussed above, TEP is our principal subsidiary and represents most of
our assets. TEP pays dividends on its common stock after its Board of Directors
declares them. TEP has certain restrictions on paying dividends, as listed
below:

     o    TEP's Credit Agreement provides that TEP can pay dividends if it
          maintains compliance with the TEP Credit Agreement and certain
          financial covenants, including a covenant that requires TEP to
          maintain a minimum level of net worth, and so long as the dividends
          and certain investments in affiliates would not exceed 65% of TEP's
          net income.

     o    The ACC order which authorized TEP to form UniSource Energy as a
          holding company provides that TEP can pay dividends so long as the
          dividends do not exceed 75% of TEP's earnings until its equity ratio
          equals 37.5% of total capital (excluding capital lease obligations).

     o    The Federal Power Act states that TEP cannot pay dividends out of
          funds that are properly included in the capital account.

     Millennium and UED have no dividend restrictions.

     UniSource Energy's principal executive offices are located at One South
Church Avenue, Suite 1820, Tucson, Arizona 85701. The telephone number is
(520) 571-4000.

                                 USE OF PROCEEDS

     As more particularly described in the prospectus supplement relating to
each issuance of Shares, we will use the net proceeds from the sale of the
Shares offered by this prospectus for general corporate purposes, including
making loans and/or capital contributions to our subsidiaries, which may include
subsidiaries to be formed for the purpose of acquiring electric and gas utility
properties in Arizona from Citizens Communications Company.

     The ACC has issued an order which, unless waived, requires that we invest
30% of any proceeds of equity issuances by UniSource Energy in TEP until TEP has
37.5% equity.


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                          DESCRIPTION OF CAPITAL STOCK

GENERAL

     The authorized capital stock of UniSource Energy presently consists of
76,000,000 shares, of which 75,000,000 shares are common stock without par
value, and 1,000,000 shares are preferred stock without par value (Preferred
Stock). As of March 31, 2003, there were 33,589,031 shares of common stock
outstanding and no shares of Preferred Stock outstanding.

     The following is a summary of certain rights and privileges of the holders
of the Shares. This summary does not purport to be complete. The following
information is qualified in its entirety by reference to UniSource Energy's
Restated Articles of Incorporation and shareholder rights plan and to the laws
of the State of Arizona.

COMMON STOCK

     Dividend Rights. UniSource Energy may pay dividends on shares of common
stock out of any funds legally available for payment, when and as declared by
our Board of Directors. Payment of dividends may be subject to certain
limitations specified with respect to the Preferred Stock, or any series of
Preferred Stock.

     Liquidation Rights. In the event of any dissolution or other winding up of
UniSource Energy, whether voluntary or involuntary, the assets of UniSource
Energy available for payment and distribution to shareholders shall be
distributed ratably in accordance with their holdings to the holders of shares
of the common stock. Those distributions may be subject to certain limitations
specified with respect to the Preferred Stock, or any series of Preferred Stock.

     Voting Rights. All voting power is vested in the holders of the common
stock, except as otherwise specified with respect to the Preferred Stock, or any
series of Preferred Stock. With respect to the election of directors and each
other matter coming before any meeting of shareholders, each holder of the
common stock shall be entitled to one (1) vote for each share of such stock
outstanding in the name of that holder on the books of UniSource Energy.

     Miscellaneous. The common stock has no preemptive or conversion rights or
redemption or sinking fund provisions and the outstanding common stock is fully
paid and non-assessable.

PREFERRED STOCK

     Our Board of Directors has authority to divide the Preferred Stock into
series and to determine the designation, preferences, and voting powers of the
shares of each series so established and the restrictions and qualifications
thereof, all to the extent and in the manner provided by law.

PREFERRED SHARE PURCHASE RIGHTS

     General. On March 5, 1999, UniSource Energy adopted a shareholder rights
plan. Under that plan, we will grant one preferred share purchase right (Right)
on each outstanding share of common stock to holders of common stock outstanding
on April 1, 1999 or issued thereafter. The description and terms of the Rights
are set forth in the Rights Agreement, dated as of March 5, 1999 (the Rights
Agreement), between UniSource Energy and The Bank of New York, as Rights Agent.
The following statements are qualified in their entirety by reference to the
Rights Agreement.


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     Each Right will entitle the registered holder, subject to regulatory
approvals and other specified conditions, to purchase one ten-thousandth of a
share of Preferred Stock, Series X, without par value, of UniSource Energy (the
Series X Preferred Stock), at a purchase price of $50.00 (the Purchase Price).

     Distribution of Rights. We have distributed one Right to shareholders of
UniSource Energy for each share of common stock owned of record by them at the
close of business on April 1, 1999. Until the earliest of:

     o    such time as any person or group acquires 15% or more of the
          outstanding shares of common stock,

     o    March 31, 2009 or

     o    the redemption of the Rights,

we will issue one Right with each share of common stock that is issued after
April 1, 1999 so that all shares of common stock will have attached Rights. We
have initially authorized and reserved 10,000 shares of Preferred Stock for
issuance upon exercise of the Rights.

     Exercise. The Rights will be exercisable only if a person or group:

     o    acquires 15% or more of the outstanding shares of common stock or

     o    commences a tender or exchange offer, the consummation of which would
          result in the beneficial ownership by a person or group of 15% or more
          of the outstanding shares of common stock.

     Until that time the Rights will be evidenced by and will trade with the
shares of common stock. The Rights will expire on March 31, 2009 unless we first
redeem or exchange them, in each case as described below.

     The purchase of stock pursuant to the Rights may be subject to regulatory
approval and other specified conditions. Under no circumstance will the person
or group that acquired 15% of the common stock be entitled to exercise Rights.

     "Flip-in". If any person or group acquires 15% or more of the outstanding
shares of common stock, each Right will entitle its holder to purchase that
number of shares of common stock or, at the option of UniSource Energy,
Preferred Stock which has a market value at that time of twice the Purchase
Price.

     "Flip-over". In addition, in the event that any person or group has
acquired 15% or more of the outstanding shares of common stock and UniSource
Energy

     o    consolidates or merges with or into, or

     o    sells 50% or more of its assets or earning power to,

any person or group, each Right would instead entitle its holder to purchase the
acquiring company's common shares having a market value of twice the Purchase
Price.


                                       5



     Exchange. If a person or group acquires more than 15% but less than 50% of
the outstanding shares of common stock, we may exchange each outstanding Right
for one share of common stock or cash, securities or other assets having a value
equal to the market value of one share of common stock. That exchange may be
subject to regulatory approval.

     Redemption. We may redeem the Rights, at a redemption price of $0.001 per
Right, at any time until any person or group has acquired 15% or more of the
outstanding shares of common stock.

     Certain Adjustments. The Purchase Price, the amount and type of securities
covered by each Right and the number of Rights outstanding will be adjusted to
prevent dilution:

     o    in the event of a stock dividend on, or a subdivision, combination or
          reclassification of, the Preferred Stock,

     o    if holders of the Preferred Stock are granted certain rights, options
          or warrants to subscribe for Preferred Stock or securities convertible
          into Preferred Stock or equivalent preferred shares at less than the
          current market price of the Preferred Stock, or

     o    upon the distribution to holders of the Preferred Stock of evidences
          of indebtedness or assets (excluding regular quarterly cash dividends)
          or of subscription rights or warrants (other than those referred to
          above).

     With certain exceptions, no adjustments in the Purchase Price will be made
until cumulative adjustments amount to a least 1% of the Purchase Price. We will
not issue fractional shares of Series X Preferred Stock other than in integral
multiples of one ten-thousandth of a share. Instead, we will make an adjustment
in cash based on the market price of the Series X Preferred Stock on the last
trading date prior to the date of exercise.

     Amendment. We may amend the Rights Agreement in any respect until any
person or group has acquired 15% or more of the outstanding shares of common
stock. Thereafter, we may amend the Rights Agreement in any manner which will
not adversely affect the holders of the Rights in any material respect.

ARIZONA BUSINESS COMBINATION STATUTE

     General. The Arizona business combination statute would limit our ability
to engage in Business Combinations with Interested Shareholders (each as defined
below).

     "Business Combination" means any (A) merger or consolidation of UniSource
Energy or any UniSource Energy subsidiary with an Interested Shareholder, (B)
exchange of shares of UniSource Energy common stock or any UniSource Energy
subsidiary for shares of an Interested Shareholder, or (C) sale, lease, transfer
or other disposition to or with an Interested Shareholder of 10% or more of the
consolidated assets of UniSource Energy.

     "Interested Shareholder" means any person other than UniSource Energy or a
UniSource Energy subsidiary that is either (A) a direct or indirect beneficial
owner of 10% or more of the voting power of the outstanding UniSource Energy
common stock or (B) an affiliate of UniSource Energy who at any time during the
three years immediately before the date in question was the beneficial owner of
10% or more of the voting power of the then outstanding UniSource Energy common
stock.


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     "Share Acquisition Date" means the date that a person first becomes an
Interested Shareholder of UniSource Energy.

     Business Combinations Within Three Years After Share Acquisition Date. For
three years after an Interested Shareholder's Share Acquisition Date, UniSource
Energy may not directly or indirectly engage in any Business Combination with an
Interested Shareholder or any affiliate of an Interested Shareholder unless,
before the Interested Shareholder's Share Acquisition Date, a committee of
disinterested directors approved either:

     o    the Business Combination; or

     o    the acquisition of common stock made by the Interested Shareholder on
          the Interested Shareholder's Share Acquisition Date.

     Business Combinations More Than Three Years After Share Acquisition Date.
If a committee of disinterested directors has not approved the Business
Combination or the acquisition of common stock as provided above, UniSource
Energy may not directly or indirectly engage in any Business Combination with an
Interested Shareholder or any affiliate of an Interested Shareholder unless:

     o    the Business Combination is consummated no earlier than three years
          after the Interested Shareholder's Share Acquisition Date, and before
          the Share Acquisition Date, the UniSource Energy Board of Directors
          approved either

          o    the Business Combination; or

          o    the acquisition of common stock made by the Interested
               Shareholder on the Share Acquisition Date; or

     o    the Business Combination is approved no earlier than three years after
          the Interested Shareholder's Share Acquisition Date by the affirmative
          vote of a majority of the outstanding voting shares of UniSource
          Energy common stock (excluding shares of common stock beneficially
          owned by the Interested Shareholder or any affiliate thereof); or

     o    the Business Combination is consummated no earlier than three years
          after the Interested Shareholder's Share Acquisition Date and meets
          certain specified conditions designed to ensure against discriminatory
          pricing.

ARIZONA CONTROL SHARE ACQUISITION STATUTE

     General. The Arizona control share acquisition statute would limit the
voting rights of a person who acquires shares of UniSource Energy under certain
circumstances in a control share acquisition (as defined below).

     Control Share Acquisition means an acquisition, directly or indirectly (in
one or more transactions within 120 days or pursuant to a plan), by a person of
beneficial ownership of shares of UniSource Energy common stock that would, but
for the limitations in the control share acquisition statute, entitle the
acquiring person to exercise a new range of voting power within the following
specified ranges: (A) at least 20% but less than 33-1/3%, (B) at least 33-1/3%
but less than or equal to 50% and (C) over 50%.


                                       7



     Information Statement. Within ten days after a Control Share Acquisition,
the acquiring person must deliver to the corporation an information statement
specifying, among other things, the range of voting power in the election of
directors that, but for the limitations in the statute, the acquiring person
believes would result from the Control Share Acquisition. At the time of
delivery of the information statement, the acquiring person may request that a
special meeting of shareholders be called to consider the voting rights of
"excess" shares (referred to below).

     Limitation on Voting Rights of "Excess" Shares. To the extent that shares
of UniSource Energy common stock acquired in a Control Share Acquisition exceed
the threshold of voting power of any of the next specified range of voting
power, such "excess" shares will have the same voting rights as other shares of
UniSource Energy common stock for election of directors but will not have the
right to vote on other matters unless approved by a shareholder resolution at an
annual or special meeting. Such resolution must be approved by the affirmative
vote of a majority of the outstanding voting shares of UniSource Energy common
stock (excluding shares owned by the acquiring person, its affiliates or any
officer or director of UniSource Energy).

     Financing Agreement. The status of voting rights of "excess" shares is not
required to be presented for consideration at any meeting of shareholders
unless, at the time of delivery of the information statement referred to above,
the acquiring person has entered into a definitive financing agreement for any
financing of the acquisition not to be provided by monies of the acquiring
person.

     Redemption by UniSource Energy. If an acquiring person fails to deliver the
required information statement within ten days after a Control Share Acquisition
or if the UniSource Energy shareholders have voted not to accord voting rights
to an acquiring person's "excess" shares referred to above, then UniSource
Energy may call for the redemption of such "excess" shares at the fair market
value of those shares at the time the call for redemption is given.

ANTITAKEOVER EFFECT

     The Rights or the provisions of Arizona Law described above, individually
or collectively, may discourage, deter, delay or impede a tender offer or other
attempt to acquire control of UniSource Energy even if the transaction would
result in the shareholders receiving a premium for their shares over current
market prices or if the shareholders otherwise believe the transaction would be
in their best interests.

                              PLAN OF DISTRIBUTION

     We may sell Shares in one or more of the following ways from time to time:
(1) directly to institutional purchasers, (2) through agents, (3) through
underwriters and/or (4) through dealers.

     The prospectus supplement will set forth the terms of each offering of
Shares, including:

     o    the names of any underwriters or agents,

     o    the purchase price of the Shares and the proceeds to UniSource Energy,
          from the sale,

     o    any underwriting discounts or agency fees and other items constituting
          underwriters'; or agents' compensation,

     o    any discounts or concessions allowed or reallowed or paid to dealers
          and


                                       8



     o    any securities exchange on which the common stock may be listed.

     If we use underwriters to sell Shares, the underwriters will acquire such
Shares for their own account and resell them from time to time in one or more
transactions, including negotiated transactions, at a fixed public offering
price or at varying prices determined at the time of sale. Unless otherwise set
forth in the applicable prospectus supplement, the obligations of the
underwriters to purchase such Shares will be subject to certain conditions
precedent, and the underwriters will be obligated to purchase all of such
securities if any of such securities are purchased, except that, in certain
cases involving a default by one or more underwriters; less than all of such
securities may be purchased. The initial public offering prices and any
discounts or concessions allowed or reallowed or paid to dealers may be changed
from time to time.

     If we use one or more agents to sell securities, the agents will be named,
and any, commissions payable by UniSource Energy to such agents will be set
forth, in the applicable prospectus supplement. Unless otherwise indicated in
the applicable prospectus supplement, any such agent will act on a best efforts
basis for the period of its appointment.




     Any agents, underwriters or dealers participating in the distribution of
the securities may be deemed to be underwriters and any discounts or commissions
received by them on the sale or resale of the securities may be deemed to be
underwriting discounts and commissions under the Securities Act of 1933, as
amended (the Securities Act). Agents and underwriters may be entitled under
agreements entered into with UniSource Energy to indemnification by UniSource
Energy, against certain liabilities, including liabilities under the Securities
Act and other securities laws, or to contribution with respect to payments that
the agents or underwriters may be required to make in respect thereof.

     The outstanding shares of UniSource Energy common stock are listed on the
New York Stock Exchange and the Pacific Exchange. Any new shares of common stock
will also be listed on those Exchanges, subject to official notice of issuance.

     Any agents, underwriters or dealers or agents participating in the
distribution of the securities, and/or affiliates thereof, may engage in
transactions with and perform services for UniSource Energy and its affiliates
in the ordinary course of business.

                       WHERE YOU CAN FIND MORE INFORMATION

AVAILABLE INFORMATION

     UniSource Energy Corporation (UniSource Energy) files reports, proxy
statements and other information with the SEC. You may read and copy this
information at the SEC's Public Reference Room at 450 Fifth Street, N.W., Room
1024, Washington, D.C. 20549. You may obtain further information on the
operation of the SEC's Public Reference Room by calling the SEC at
1-800-SEC-0330. The SEC also maintains an Internet site that contains reports,
proxy statements and other information about issuers, such as UniSource Energy,
who file electronically with the SEC. The address of that site is
http://www.sec.gov.

     You can also inspect reports, proxy statements and other information
concerning UniSource Energy at the offices of the New York Stock Exchange at 20
Broad Street, New York, New York 10005 or the Pacific Exchange, Inc. at 301 Pine
Street, San Francisco, California 94104. You may also obtain information from
the UniSource Energy Internet site at http://www.unisourceenergy.com. The
information on our website is not incorporated by reference into this prospectus
and you should not consider it a part of this prospectus.


                                       9



INCORPORATION BY REFERENCE


     The rules of the SEC allow us to "incorporate by reference" information
into this prospectus, which means that we can disclose important information to
you by referring you to another document filed separately with the SEC. The
information incorporated by reference is deemed to be part of this prospectus,
and later information that we file with the SEC will automatically update and
supersede that information. The prospectus incorporates by reference the
documents set forth below that have been previously filed with the SEC. These
documents contain important information about UniSource Energy.

     o    Annual Report on Form 10-K for the year ended December 31, 2002

     o    Current Report on Form 8-K dated April 11, 2003

     We are also incorporating by reference additional documents that UniSource
Energy files with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the
Securities Exchange Act of 1934, as amended (the Exchange Act), after the date
of this prospectus and all documents that UniSource Energy files with the SEC
pursuant to the Exchange Act after the date of the initial registration
statement and prior to the effectiveness of the registration statement;
provided,  however,  that any  information  furnished under Items 9 or 12 of any
Current Report on Form 8-K shall not be deemed incorporated by reference herein.


     UniSource Energy will provide without charge to each person, including any
beneficial owner, to whom a copy of this prospectus has been delivered a copy of
any and all of these filings. You may request a copy of these filings by writing
or telephoning us at UniSource Energy Corporation, P.O. Box 711, Tucson, Arizona
85702, Attention: Records and Library Services, Telephone: (520) 745-3349.


                                       10



                           FORWARD-LOOKING STATEMENTS

     This prospectus and the documents incorporated by reference in this
prospectus contain forward-looking statements as defined by the Private
Securities Litigation Reform Act of 1995. UniSource Energy is including the
following cautionary statements to make applicable and take advantage of the
safe harbor provisions of the Private Securities Litigation Reform Act of 1995
for any forward-looking statements made by or for UniSource Energy in this
prospectus. Forward-looking statements include statements concerning plans,
objectives, goals, strategies, future events or performance and underlying
assumptions and other statements that are not statements of historical facts.
Forward-looking statements may be identified by the use of words such as
"anticipates," "estimates," "expects," "intends," "plans," "predicts,"
"projects," and similar expressions. All such forward-looking statements,
whether written or oral, and whether made by or on behalf of UniSource Energy,
are expressly qualified by these cautionary statements and any other cautionary
statements which may accompany the forward-looking statements. In addition,
UniSource Energy disclaims any obligation to update any forward-looking
statements to reflect events or circumstances after the date of this prospectus.

     Forward-looking statements involve risks and uncertainties that could cause
actual results or outcomes to differ materially from those expressed in the
forward-looking statements. We express our expectations, beliefs and projections
in good faith and believe them to have a reasonable basis. However, we make no
assurances that management's expectations, beliefs or projections will be
achieved or accomplished. We have identified the following important factors
that could cause actual results to differ materially from those discussed in our
forward-looking statements. These may be in addition to other factors and
matters discussed in other parts of this prospectus:

     1.   Effects of restructuring initiatives in the electric industry and
          other energy-related industries.

     2.   Effects of competition in retail and wholesale energy markets.

     3.   Changes in economic conditions, demographic patterns and weather
          conditions in TEP's retail service area.

     4.   Supply and demand conditions in wholesale energy markets, including
          volatility in market prices and illiquidity in markets, which are
          affected by a variety of factors. These factors include the
          availability of generating capacity in the western U.S., including
          hydroelectric resources, weather, natural gas prices, the extent of
          utility restructuring in various states, transmission constraints,
          environmental restrictions and cost of compliance, and FERC regulation
          of wholesale energy markets.

     5.   The creditworthiness of the entities with whom UniSource Energy, TEP,
          Millennium and their affiliates transact business.

     6.   Changes affecting TEP's cost of providing electrical service including
          changes in fuel costs, generating unit operating performance,
          scheduled and unscheduled plant outages, interest rates, tax laws,
          environmental laws, and the general rate of inflation.

     7.   Changes in governmental policies and regulatory actions with respect
          to financing and rate structures.

     8.   Changes affecting the cost of competing energy alternatives, including
          changes in available generating technologies and changes in the cost
          of natural gas.


                                       11



     9.   Changes in accounting principles or the application of such principles
          to UniSource Energy or TEP.

     10.  Market conditions and technological changes affecting UniSource
          Energy's unregulated businesses.

     11.  Regulatory conditions to the approval of the acquisition of Citizens'
          Arizona electric utility and gas utility assets.

     12.  The level of rate relief granted with respect to Citizens' Arizona
          electric utility and gas utility assets.

     13.  Unanticipated changes in future liabilities relating to employee
          benefit plans due to changes in market values of its retirement plan
          assets and health care costs.

     14.  The outcome of any ongoing litigation.

     15.  Ability to obtain financing through debt and/or equity issuance, which
          can be affected by various factors, including interest rate
          fluctuations and capital market conditions.

     16.  Whether the proposed Springerville Generating Station expansion
          proceeds; the role of Tri-State, SRP, and other third parties in such
          expansion; and the terms of the ownership, operating and power
          purchase arrangements ultimately utilized.

                                     EXPERTS


     The consolidated financial statements incorporated in this prospectus by
reference to the Annual Report on Form 10-K for the year ended December 31,
2002, have been so incorporated in reliance on the report of
PricewaterhouseCoopers LLP, independent accountants, given on the authority of
said firm as experts in auditing and accounting.





                                  LEGAL MATTERS

     The validity of the Shares will be passed upon for UniSource Energy by
Thelen Reid & Priest LLP, our special counsel, and Vincent Nitido, Jr., Esq.,
our Vice President and General Counsel, and for any agents, underwriters or
dealers by counsel to be identified in the applicable prospectus supplement. In
giving their opinions, Thelen Reid & Priest LLP and counsel for any agents,
underwriters or dealers may rely, as to matters of Arizona law, upon the opinion
of Mr. Nitido.


                                       12



                                     PART II
                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 16.  EXHIBITS

     Reference is made to the Exhibit Index on page II-3 hereof.

                                   SIGNATURES


     Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-3 and has duly caused this amendment to the
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized to sign, in the City of Tucson, and the State of Arizona, on
May 9, 2003.


                                          UNISOURCE ENERGY CORPORATION



                                          By:  /s/ Kevin P. Larson
                                               ---------------------------------
                                               KEVIN P. LARSON
                                               Vice President, Principal
                                               Financial Officer and Treasurer


     Pursuant to the requirements of the Securities Act of 1933, this amendment
to the Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.


Date:  May 9, 2003                        *
                                          --------------------------------------
                                          James S. Pignatelli
                                          Chairman of the Board, President and
                                          Principal Executive Officer

Date:  May 9, 2003                        /s/ Kevin P. Larson
                                          --------------------------------------
                                          Kevin P. Larson
                                          Vice President, Principal Financial
                                          Officer and Treasurer

Date:  May 9, 2003                        *
                                          --------------------------------------
                                          Karen G. Kissinger
                                          Vice President and Principal
                                          Accounting Officer

Date:  May 9, 2003                        *
                                          --------------------------------------
                                          Lawrence J. Aldrich
                                          Director

Date:  May 9, 2003                        *
                                          --------------------------------------
                                          Larry W. Bickle
                                          Director

Date:  May 9, 2003                        *
                                          --------------------------------------
                                          Elizabeth T. Bilby
                                          Director


                                      II-1



Date:  May 9, 2003                        *
                                          --------------------------------------
                                          Harold W. Burlingame
                                          Director

Date:  May 9, 2003                        *
                                          --------------------------------------
                                          John L. Carter
                                          Director

Date:  May 9, 2003                        *
                                          --------------------------------------
                                          Daniel W.L. Fessler
                                          Director

Date:  May 9, 2003                        *
                                          --------------------------------------
                                          Kenneth Handy
                                          Director

Date:  May 9, 2003                        *
                                          --------------------------------------
                                          Warren Y. Jobe
                                          Director

Date:  May 9, 2003                        *
                                          --------------------------------------
                                          H. Wilson Sundt
                                          Director



*By:  /s/ Kevin P. Larson
     -----------------------------
      Kevin P. Larson
      Attorney-in-fact


                                      II-2



                                  EXHIBIT INDEX
                                  -------------


Exhibit No.             Description of Exhibit
-----------             ----------------------

          1       --    Form of Underwriting Agreement with respect to Common
                        Stock (A form will be filed as an exhibit to a report on
                        Form 8-K, as contemplated by Item 601(b)(1) of
                        Regulation S-K under the Securities Act, or by
                        amendment.)

*         4(a)    --    Amended and Restated Articles of Incorporation (filed
                        with the Commission on January 30, 1998, as Exhibit 2(a)
                        to Registrant's Amendment No. 1 to Form 8-A and
                        incorporated herein by reference thereto).

*         4(b)    --    Bylaws (filed with the Commission on December 23, 1997
                        as Exhibit 2(b) to Registrant's Form 8-A and
                        incorporated herein by reference thereto).

*         4(c)    --    Rights Agreement, dated as of March 5, 1999, between
                        UniSource Energy Corporation and The Bank of New York,
                        as Rights Agent (filed with the Commission on March 5,
                        1999, as Exhibit 4 to Registrant's Form 8-K dated
                        March 5, 1999, and incorporated herein by reference
                        thereto).

          5(a)    --    Opinion of Vincent Nitido, Jr., Esq.

          5(b)    --    Opinion of Thelen Reid & Priest LLP.




          23(a)   --    The Consents of Vincent Nitido, Jr., Esq. and Thelen
                        Reid & Priest LLP are contained in their opinions as
                        Exhibits 5(a) and 5(b), respectively.


*         23(b)   --    Consent of PricewaterhouseCoopers LLP.


**        24      --    Power of Attorney is contained at page II-4 of the
                        initial filing of the Registration Statement.


-------------------

*    Previously filed as indicated and incorporated herein by reference.

**   Previously filed with the initial filing of the Registration Statement on
     February 21, 2003.


                                      II-3