UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549


SCHEDULE 13G
Under the Securities Exchange Act of 1934



Amendment No.: 2*


Name of Issuer: Alexion Pharmaceuticals, Inc.


Title of Class of Securities:  Common Stock


CUSIP Number:  01535110-9



*The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which
would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 ("Act") or otherwise subject to the liabilities of that section
of the Act but shall be subject to all other provisions of the Act (however,
see the Notes).

All share information contained in this filing, as it pertains to this
issuer, is as of March 31, 2001.

CUSIP No.: 01535110-9                            Page 2 of 8

1.  NAME OF REPORTING PERSON
         S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
         Janus Capital Corporation
         EIN #84-0765359

2.  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
         a.   ___
         b.   _X_

3.  SEC USE ONLY

4.  CITIZENSHIP OR PLACE OF ORGANIZATION
         Colorado

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

    5.   SOLE VOTING POWER
              1,201,225**

    6.   SHARED VOTING POWER
              -0-

    7.   SOLE DISPOSITIVE POWER
              1,201,225**

    8.   SHARED DISPOSITIVE POWER
              -0-

9.  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
         1,201,225**

10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
         N/A

11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
         6.7%**

12. TYPE OF REPORTING PERSON
         IA, CO

**  See Item 4 of this filing

CUSIP No.:  01535110-9                           Page 3 of 8

1.  NAME OF REPORTING PERSON
         S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON
         Thomas H. Bailey

2.  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
         a.   ___
         b.   _X_

3.  SEC USE ONLY

4.  CITIZENSHIP OR PLACE OF ORGANIZATION
         USA

NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH:

    5.   SOLE VOTING POWER
              1,201,225**

    6.   SHARED VOTING POWER
              -0-

    7.   SOLE DISPOSITIVE POWER
              1,201,225**

    8.   SHARED DISPOSITIVE POWER
              -0-

9.  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
         1,201,225**

10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
         N/A

11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
         6.7%**

12. TYPE OF REPORTING PERSON
         IN
**  See Item 4 of this filing

SCHEDULE 13G                                          Page 4 of 8

Item 1.

    (a). Name of Issuer: Alexion Pharmaceuticals, Inc. ("Alexion
         Pharmaceuticals ")

    (b). Address of Issuer's Principal Executive Offices:

         352 Knotter Drive
         Cheshire, CT 06410

Item 2.

    (a).-(c). Name, Principal Business Address, and Citizenship of Persons
              Filing:

         (1)  Janus Capital Corporation ("Janus Capital")
              100 Fillmore Street
              Denver, Colorado  80206-4923
              Citizenship:  Colorado

         (2)  Thomas H. Bailey ("Mr. Bailey")
              100 Fillmore Street
              Denver, Colorado  80206-4923
              Citizenship:  USA

    (d). Title of Class of Securities:  Common Stock

    (e). CUSIP Number:  01535110-9

Item 3.

    Janus Capital is an Investment Adviser registered under Section 203 of the
    Investment Advisers Act of 1940.

SCHEDULE 13G                                          Page 5 of 8

Item 4.  Ownership

         The information in items 1 and 5 through 11 on the cover pages (pp. 2-
         3) on Schedule 13G is hereby incorporated by reference.

         Janus Capital is a registered investment adviser which furnishes
         investment advice to several investment companies registered under
         Section 8 of the Investment Company Act of 1940 and individual and
         institutional clients (collectively referred to herein as "Managed
         Portfolios").  As a result of its role as investment adviser or sub-
         adviser to the Managed Portfolios, Janus Capital may be deemed to be
         the beneficial owner of the shares of Alexion Pharmaceuticals  Common
         Stock  held by such Managed Portfolios.  However, Janus Capital does
         not have the right to receive any dividends from, or the proceeds from
         the sale of, the securities held in the Managed Portfolios and
         disclaims any ownership associated with such rights.

         Mr. Bailey owns approximately 12.2% of Janus Capital.  In addition to
         being a stockholder of Janus Capital, Mr. Bailey serves as President
         and Chairman of the Board of Janus Capital and is filing this joint
         statement with Janus Capital as a result of such stock ownership and
         positions which may be deemed to enable him to exercise control over
         Janus Capital.  Mr. Bailey does not own of record any shares of
         Alexion Pharmaceuticals  Common Stock  and he has not engaged in any
         transaction in Alexion Pharmaceuticals  Common Stock .  However, as a
         result of his position, Mr. Bailey may be deemed to have the power to
         exercise or to direct the exercise of such voting and/or dispositive
         power that Janus Capital may have with respect to Alexion
         Pharmaceuticals  Common Stock  held by the Managed Portfolios.  All
         shares reported herein have been acquired by the Managed Portfolios,
         and Mr. Bailey specifically disclaims beneficial ownership over any
         shares of Alexion Pharmaceuticals  Common Stock  that he or Janus
         Capital may be deemed to beneficially own.  Furthermore, Mr. Bailey
         does not have the right to receive any dividends from, or the proceeds
         from the sale of, the securities held in the Managed Portfolios and
         disclaims any ownership associated with such rights.

SCHEDULE 13G                                          Page 6 of 8

Item 5.  Ownership of Five Percent or Less of a Class

              N/A

Item 6.  Ownership of More than Five Percent on Behalf of Another Person

              Janus Capital's Managed Portfolios, set forth in Item 4 above,
              have the right to receive all dividends from, and the proceeds
              from the sale of, the securities held in their respective
              accounts.

              The interest of any one such person does not exceed 5% of the
              class of securities.

              These shares were acquired in the ordinary course of business,
              and not with the purpose of changing or influencing control of
              the Issuer.

Item 7.  Identification and Classification of the Subsidiary Which
         Acquired the Security Being Reported on by the Parent Holding
         Company

              N/A

Item 8.  Identification and Classification of Members of the Group

              N/A

Item 9.  Notice of Dissolution of Group

              N/A

Item 10.      Certification

              By signing below I certify that, to the best of my knowledge and
              belief, the securities referred to above were acquired in the
              ordinary course of business and were not acquired for the purpose
              of and do not have the effect of changing or influencing the
              control of the issuer of such securities and were not acquired in
              connection with or as a participant in any transaction having
              such purposes or effect.

SCHEDULE 13G                                          Page 7 of 8

SIGNATURES

    After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete
and correct.

JANUS CAPITAL CORPORATION

By  /s/  Heidi J. Walter                       04/09/01
  Heidi J. Walter,                                  Date
    Vice President and Assistant General Counsel

THOMAS H. BAILEY

By  /s/  Heidi J. Walter                       04/09/01
  Heidi J. Walter                                   Date

  Under Power of Attorney dated 6/5/00
  On file with Schedule 13G
  for Powertel, Inc. 6/8/00

SCHEDULE 13G                                        Page 8 of 8

EXHIBIT A

JOINT FILING AGREEMENT

  In accordance with Rule 13d-1(f) under the Securities Exchange Act of 1934,
the persons named below agree to the joint filing on behalf of each of them
of a Statement on Schedule 13G (including amendments thereto) with respect to
the Common Stock  of Alexion Pharmaceuticals, Inc. and further agree that
this Joint Filing Agreement be included as an Exhibit to such joint filings.
In evidence thereof, the undersigned hereby execute this Agreement as of the
9th day of April, 2001.

            JANUS CAPITAL CORPORATION

            By  /s/  Heidi J. Walter
               Heidi J. Walter,
                 Vice President and Assistant General Counsel

            THOMAS H. BAILEY

  By  /s/  Heidi J. Walter
               Heidi J. Walter

               Under Power of Attorney dated 6/5/00
               On file with Schedule 13G
               for Powertel, Inc. 6/8/00