UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              Washington, DC 20549
                                   FORM 10-K/A
                (X) ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

                   FOR THE FISCAL YEAR ENDED DECEMBER 31, 2002
                                       OR
              ( ) Transition report pursuant to Section 13 or 15(d)
                     of the Securities Exchange Act of 1934
                   For the transition period from     to    .

                         COMMISSION FILE NUMBER 1-14756

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


                                                                               
                           Missouri                                                            43-1723446
(State or other jurisdiction of incorporation or organization)                    (I.R.S. Employer Identification No.)


                 1901 Chouteau Avenue, St. Louis, Missouri 63103
              (Address of principal executive offices and Zip Code)

       Registrant's telephone number, including area code: (314) 621-3222

           SECURITIES REGISTERED PURSUANT TO SECTION 12(b) OF THE ACT:



        Title of each class                           Name of each exchange on which registered
        -------------------                           -----------------------------------------
                                                   
Common Stock, $ .01 par value and                                 New York Stock Exchange
   Preferred Share Purchase Rights
Normal Units                                                      New York Stock Exchange


        SECURITIES REGISTERED PURSUANT TO SECTION 12(g) OF THE ACT: NONE.

     Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes (X). No ( ).

     Indicate by check mark if disclosure of delinquent filers pursuant to Item
405 of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K. ( ).

     Indicate by check mark whether the registrant is an accelerated filer (as
defined in Rule 12b-2 of the Securities Exchange Act of 1934). Yes (X). No ( ).

     As of June 28, 2002, the registrant had 144,774,189 shares of its $.01 par
value common stock outstanding. The aggregate market value of these shares of
common stock (based upon the closing price of these shares on the New York Stock
Exchange on that date) held by non-affiliates was $301,580,783.

     As of March 21, 2003, the registrant had 160,720,970 shares of its $.01 par
value common stock outstanding.

                      DOCUMENTS INCORPORATED BY REFERENCE:

     Portions of the registrant's 2002 Annual Report to Shareholders (the 2002
Annual Report) are incorporated by reference into Parts I, II and IV. The
registrant's consolidated financial statements for the fiscal year ended
December 31, 2002, including the notes thereto, and the Management's Discussion
and Analysis of Financial Condition and Results of Operations for the
registrant, contained in the portions of the 2002 Annual Report incorporated by
reference herein were also filed with the Commission by the registrant on its
Current Report on Form 8-K dated March 5, 2003.

         Portions of the registrant's definitive proxy statement for the 2003
annual meeting of shareholders are incorporated by reference into Part III.





                                EXPLANATORY NOTE

         All documents identified as being filed with our Form 10-K for the
fiscal year ended December 31, 2002 were filed except Exhibit No. 13.1 "Those
pages of the 2002 Annual Report incorporated herein by reference" which is being
filed with this amendment to Form 10-K.

                                     PART IV

ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K

     (C)  Exhibits

         EXHIBIT NO.                          DESCRIPTION

         2.1          Stock purchase agreement, dated as of April 28, 2002, by
                      and between The AES Corporation (AES) and Ameren (March
                      31, 2002 Form 10-Q, Exhibit 2.1).

         2.2          Membership Interest Purchase Agreement, dated as of April
                      28, 2002, by and between AES and Ameren (March 31, 2002
                      Form 10-Q, Exhibit 2.2).

         3.1(i)       Restated Articles of Incorporation of Ameren (File No.
                      33-64165, Annex F).

         3.2(i)       Certificate of Amendment to Ameren's Restated Articles of
                      Incorporation filed with the Secretary of State of the
                      State of Missouri on December 14, 1998 (1998 Form 10-K,
                      Exhibit 3(i)).

         3.3(ii)      By-Laws of Ameren as amended to December 31, 1997 (1997
                      Form 10-K, Exhibit 3(ii)).

         4.1          Indenture of Mortgage and Deed of Trust of AmerenUE dated
                      June 15, 1937 (AmerenUE Mortgage), as amended May 1, 1941,
                      and Second Supplemental Indenture dated May 1, 1941 (File
                      No. 2-4940, Exhibit B-1).

         4.2          Supplemental Indentures to the AmerenUE Mortgage



                      DATED AS OF                   FILE REFERENCE                       EXHIBIT NO.
                      -----------                   --------------                       -----------
                                                                                   
                      April 1, 1971          AmerenUE Form 8-K, April 1971                    6
                      February 1, 1974       AmerenUE Form 8-K, February 1974                 3
                      July 7, 1980           2-69821                                          4.6
                      December 1, 1991       33-45008                                         4.4
                      December 4, 1991       33-45008                                         4.5
                      January 1, 1992        AmerenUE Form 10-K, 1991                         4.6
                      October 1, 1992        AmerenUE Form 10-K, 1992                         4.6
                      December 1, 1992       AmerenUE Form 10-K, 1992                         4.7
                      February 1, 1993       AmerenUE Form 10-K, 1992                         4.8
                      May 1, 1993            AmerenUE Form 10-K, 1993                         4.6
                      August 1, 1993         AmerenUE Form 10-K, 1993                         4.7
                      October 1, 1993        AmerenUE Form 10-K, 1993                         4.8
                      January 1, 1994        AmerenUE Form 10-K, 1993                         4.9
                      February 1, 2000       AmerenUE Form 10-K, 2000                         4.1
                      August 15, 2002        AmerenUE Form 8-K, August 22, 2002               4.3
                      March 5, 2003          AmerenUE Form 8-K, March 10, 2003                4.4


         4.3          Indenture (for unsecured subordinated debt securities) of
                      AmerenUE dated as of December 1, 1996 (AmerenUE 1996 Form
                      10-K, Exhibit 4.36).

         4.4          Loan Agreement dated as of December 1, 1991 between the
                      State Environmental Improvement and Energy Resources
                      Authority and AmerenUE, together with Indenture of Trust
                      dated as of December 1, 1991 between the Authority and UMB
                      Bank, N.A. as successor trustee to Mercantile Bank of St.
                      Louis, N.A. (AmerenUE 1992 Form 10-K, Exhibit 4.37).


                                       2


      EXHIBIT NO.                       DESCRIPTION

         4.5          Loan Agreement dated as of December 1, 1992, between the
                      State Environmental Improvement and Energy Resources
                      Authority and AmerenUE, together with Indenture of Trust
                      dated as of December 1, 1992 between the Authority and UMB
                      Bank, N.A. as successor trustee to Mercantile Bank of St.
                      Louis, N.A. (AmerenUE 1992 Form 10-K, Exhibit 4.38).

         4.6          Fuel Lease dated as of February 24, 1981 between AmerenUE,
                      as lessee, and Gateway Fuel Company, as lessor, covering
                      nuclear fuel (AmerenUE 1980 Form 10-K, Exhibit 10.20).

         4.7          Amendments to Fuel Lease dated as of May 8, 1984 and
                      October 15, 1984, respectively, between AmerenUE, as
                      lessee, and Gateway Fuel Company, as lessor, covering
                      nuclear fuel (File No. 2-96198, Exhibit 4.28).

         4.8          Amendment to Fuel Lease dated as of October 15, 1986
                      between AmerenUE, as lessee, and Gateway Fuel Company, as
                      lessor, covering nuclear fuel (AmerenUE September 30, 1986
                      Form 10-Q, Exhibit 4.3).

         4.9          Series 1998A Loan Agreement dated as of September 1, 1998
                      between The State Environmental Improvement and Energy
                      Resources Authority of the State of Missouri and AmerenUE
                      (AmerenUE September 30, 1998 Form 10-Q, Exhibit 4.28).

         4.10         Series 1998B Loan Agreement dated as of September 1, 1998
                      between The State Environmental Improvement and Energy
                      Resources Authority of the State of Missouri and AmerenUE
                      (AmerenUE September 30, 1998 Form 10-Q, Exhibit 4.29).

         4.11         Series 1998C Loan Agreement dated as of September 1, 1998
                      between The State Environmental Improvement and Energy
                      Resources Authority of the State of Missouri and AmerenUE
                      (AmerenUE September 30, 1998 Form 10-Q, Exhibit 4.30).

         4.12         Indenture dated as of August 15, 2002 from AmerenUE to The
                      Bank of New York, as Trustee, relating to senior secured
                      debt securities (including the forms of senior secured
                      debt securities as exhibits) (Ameren UE Form 8-K dated
                      August 22, 2002, Exhibit 4.1).

         4.13         AmerenUE Company order dated August 22, 2002 establishing
                      the 5.25% Senior Secured Notes due 2012 (AmerenUE Form 8-K
                      dated August 22, 2002, Exhibit 4.2).

         4.14         AmerenUE Company order dated March 10, 2003 establishing
                      the 5.50% Senior Secured Notes due 2034 (AmerenUE Form 8-K
                      dated March 10, 2003, Exhibit 4.2).

         4.15         Indenture of Mortgage or Deed of Trust dated October 1,
                      1941, from Central Illinois Public Service Company d/b/a
                      AmerenCIPS (AmerenCIPS) to Continental Illinois National
                      Bank and Trust Company of Chicago and Edmond B. Stofft, as
                      Trustees (U.S. Bank Trust National Association and Patrick
                      J. Crowley are successor Trustees.) (Exhibit 2.01 in File
                      No. 2-60232).

         4.16         Supplemental Indentures dated, respectively September 1,
                      1947, January 1, 1949, February 1, 1952, September 1,
                      1952, June 1, 1954, February 1, 1958, January 1, 1959, May
                      1, 1963, May 1, 1964, June 1, 1965, May 1, 1967, April 1,
                      1970, April 1, 1971, September 1, 1971, May 1, 1972,
                      December 1, 1973, March 1, 1974, April 1, 1975, October 1,
                      1976, November 1, 1976, October 1, 1978, August 1, 1979,
                      February 1, 1980, February 1, 1986, May 15, 1992, July 1,
                      1992, September 15, 1992, April 1, 1993, June 1, 1995,
                      March 15, 1997, June 1, 1997, December 1, 1998 and June 1,
                      2001 between AmerenCIPS and the Trustees under the
                      Indenture of Mortgage or Deed of Trust referred to above
                      as Exhibit 4.14 (Amended Exhibit 7(b) in File No. 2-7341;
                      Second Amended Exhibit 7.03 in File No. 2-7795; Second
                      Amended Exhibit 4.07 in File No. 2-9353; Amended Exhibit
                      4.05 in File No. 2-9802; Amended Exhibit 4.02 in File No.
                      2-10944; Amended Exhibit 2.02 in File No. 2-13866; Amended
                      Exhibit 2.02 in File No. 2-14656; Amended Exhibit 2.02 in
                      File No.2-21345; Amended Exhibit 2.02 in File No. 2-22326;
                      Amended Exhibit 2.02 in File No. 2-23569; Amended Exhibit
                      2.02 in File No. 2-26284; Amended Exhibit 2.02 in File No.
                      2-36388; Amended Exhibit 2.02 in File No. 2-39587; Amended
                      Exhibit 2.02 in File No. 2-41468; Amended Exhibit 2.02 in
                      File No. 2-43912; Exhibit 2.03 in File No. 2-60232;
                      Amended Exhibit 2.02 in File No. 2-50146; Amended Exhibit
                      2.02 in File No. 2-52886; Second Amended Exhibit 2.04 in
                      File No. 2-57141; Amended Exhibit 2.04 in File No.
                      2-57557;


                                       3


         EXHIBIT NO.                           DESCRIPTION

                      Amended Exhibit 2.06 in File No. 2-62564; Exhibit 2.02(a)
                      in File No. 2-65914; Amended Exhibit 2.02(a) in File No.
                      2-66380; and Amended Exhibit 4.02 in File No. 33-3188;
                      Exhibit 4.02 to AmerenCIPS Form 8-K dated May 15, 1992;
                      Exhibit 4.02 to AmerenCIPS Form 8-K dated July 1, 1992;
                      Exhibit 4.02 to AmerenCIPS Form 8-K dated September 15,
                      1992; Exhibit 4.02 to AmerenCIPS Form 8-K dated March 30,
                      1993; Exhibit 4.03 to AmerenCIPS Form 8-K dated June 5,
                      1995; Exhibit 4.03 to AmerenCIPS Form 8-K dated March 15,
                      1997; Exhibit 4.03 to AmerenCIPS Form 8-K dated June 1,
                      1997; Exhibit 4.2 in File No. 333-59438; Exhibit 4.1 to
                      June 30, 2001 AmerenCIPS Form 10-Q.)

         4.17         Agreement, dated as of October 9, 1998, between Ameren and
                      EquiServe Trust Company, N.A. (as successor to First
                      Chicago Trust Company of New York), as Rights Agent, which
                      includes the form of Certificate of Designation of the
                      Preferred Shares as Exhibit A, the form of Rights
                      Certificate as Exhibit B and the Summary of Rights as
                      Exhibit C (October 14, 1998 Form 8-K, Exhibit 4).

         4.18         Indenture dated as of December 1, 1998 from AmerenCIPS to
                      The Bank of New York, as Trustee, relating to AmerenCIPS'
                      Senior Notes, 5.375% due 2008 and 6.125% due 2028 (Exhibit
                      4.4, in File No. 333-59438).

         4.19         Indenture dated as of November 1, 2000 from AmerenEnergy
                      Generating Company (Generating Company) to The Bank of New
                      York, as Trustee, relating to the issuance of senior notes
                      (File No. 333-56594, Exhibit 4.1).

         4.20         First Supplemental Indenture dated as of November 1, 2000
                      to Indenture dated as of November 1, 2000 from Generating
                      Company to The Bank of New York, as Trustee, relating to
                      Generating Company's 7.75% Senior Notes, Series A due 2005
                      and 8.35% Senior Notes, Series B due 2010 (File No.
                      333-56594, Exhibit 4.2).

         4.21         Form of Second Supplemental Indenture dated as of June 12,
                      2001 to Indenture dated as of November 1, 2000 from
                      Generating Company to The Bank of New York, as Trustee,
                      relating to Generating Company's 7.75% Senior Notes,
                      Series C due 2005 and 8.35% Senior Note, Series D due 2010
                      (including as exhibit the form of Exchange Note) (File No.
                      333-56594, Exhibit 4.3).

         4.22         Third Supplemental Indenture dated as of June 1, 2002 to
                      Indenture dated as of November 1, 2000 from Generating
                      Company to The Bank of New York, as Trustee, relating to
                      Generating Company's 7.95% Senior Notes, Series E due 2032
                      (including as exhibit the form of Note) (June 30, 2002
                      Generating Company Form 10-Q, Exhibit 4.1).

         4.23         Fourth Supplemental Indenture dated as of January 15, 2003
                      to Indenture dated as of November 1, 2000 from Generating
                      Company to The Bank of New York, as Trustee, relating to
                      Generating Company's 7.95% Senior Notes, Series F due 2032
                      (including as exhibit the form of Exchange Note)
                      (Generating Company 2002 Form 10-K, Exhibit 4.5).

         4.24         Indenture of Ameren with The Bank of New York, as Trustee,
                      relating to senior debt securities dated as of December 1,
                      2001 (Ameren's Senior Indenture) (File No. 333-81774,
                      Exhibit 4.5).

         4.25         Ameren company order relating to $150 million Floating
                      Rate Notes due December 12, 2003 issued under Ameren's
                      Senior Indenture (including the forms of notes) (File No.
                      333-81774, Exhibit 4.6).

         4.26         Ameren company order relating to $100 million 5.70% Notes
                      due February 1, 2007 issued under Ameren's Senior
                      Indenture (including the forms of notes) (File No.
                      333-81774, Exhibit 4.7).

         4.27         Ameren company order relating to $345 million Notes due
                      May 15, 2007 issued under Ameren's Senior Indenture
                      (including the forms of notes and certificate of normal
                      unit) (File No. 333-81774, Exhibit 4.8).

         4.28         Purchase Contract Agreement dated as of March 1, 2002
                      between Ameren and The Bank of New York, as purchase
                      contract agent, relating to the 13,800,000 9.75%
                      Adjustable Conversion-Rate Equity Security Units (Equity
                      Security Units) (File No. 333-81774, Exhibit 4.15).


                                       4



      EXHIBIT NO.                    DESCRIPTION

         4.29         Pledge Agreement dated as of March 1, 2002 among Ameren,
                      The Bank of New York, as purchase contract agent and BNY
                      Trust Company of Missouri, as collateral agent, custodial
                      agent and securities intermediary, relating to the Equity
                      Security Units (File No. 333-81774, Exhibit 4.16).

         4.30         Indenture, dated as of October 18, 1999, between Midwest
                      Energy, Inc and The Bank of New York, as Trustee; First
                      Supplemental Indenture, dated as of October 18, 1999,
                      between CILCORP Inc. and The Bank of New York (Designated
                      in registration statement Form S-4 filed by CILCORP, Inc.
                      (CILCORP) on November 4, 1999, as exhibits 4.1 and 4.2).

         4.31         Indenture of Mortgage and Deed of Trust between Illinois
                      Power Company and Bankers Trust Company, as Trustee, dated
                      as of April 1, 1933, Supplemental Indenture between the
                      same parties dated as of June 30, 1933, Supplemental
                      Indenture between the Company and Bankers Trust Company,
                      as Trustee, dated as of July 1, 1933 and Supplemental
                      Indenture between the same parties dated as of January 1,
                      1935, securing First Mortgage Bonds, and indentures
                      supplemental to the foregoing through November 1, 1994.
                      (Designated in Registration No. 2-1937 as Exhibit B-1, in
                      Registration No. 2-2093 as Exhibit B-1(a), in Form 8-K for
                      April 1940, File No. 1-2732-2, as Exhibit A, in Form 8-K
                      for December 1949, File No. 1-2732-2, as Exhibit A, in
                      Form 8-K for December 1951, File No. 1-2732, as Exhibit A,
                      in Form 8-K for July 1957, File No. 1-2732, as Exhibit A,
                      in Form 8-K for July 1958, File No. 1-2732, as Exhibit A,
                      in Form 8-K for March 1960, File No. 1-2732, as Exhibit A,
                      in Form 8-K for September 1961, File No. 1-2732, as
                      Exhibit B, in Form 8-K for March 1963, File No. 1-2732, as
                      Exhibit A, in Form 8-K for February 1966, File No. 1-2732,
                      as Exhibit A, in Form 8-K for March 1967, File No. 1-2732,
                      as Exhibit A, in Form 8-K for August 1970, File No.
                      1-2732, as Exhibit A, in Form 8-K for September 1971, File
                      No. 1-2732, as Exhibit A, in Form 8-K for September 1972,
                      File No. 1-2732, as Exhibit A, in Form 8-K for April 1974,
                      File No. 1-2732, as Exhibit 2(b), in Form 8-K for June
                      1974, File No. 1-2732, as Exhibit A, in Form 8-K for March
                      1975, File No. 1-2732, as Exhibit A, in Form 8-K for May
                      1976, File No. 1-2732, as Exhibit A, in Form 10-Q for the
                      quarter ended June 30, 1978, File No. 1-2732, as Exhibit
                      2, in Form 10-K for the year ended December 31, 1982, File
                      No. 1-2732, as Exhibit (4)(b), in Form 8-K dated January
                      30, 1992, File No. 1-2732, as Exhibit (4) in Form 8-K
                      dated January 29, 1993, File No. 1-2732, as Exhibit (4)
                      and in Form 8-K dated December 2, 1994, File No. 1-2732,
                      as Exhibit (4).)

         10.1      *  Ameren's Long-Term Incentive Plan of 1998 (1998 Form
                      10-K, Exhibit 10.1).

         10.2      *  Ameren's Change of Control Severance Plan (1998 Form
                      10-K, Exhibit 10.2).

         10.3      *  Ameren's Deferred Compensation Plan for Members of the
                      Board of Directors (1998 Form 10-K, Exhibit 10.4).

         10.4      *  Ameren's Deferred Compensation Plan for Members of the
                      Ameren Leadership Team as amended and restated effective
                      January 1, 2001 (2000 Form 10-K, Exhibit 10.1).

         10.5      *  Ameren's Executive Incentive Compensation Program Elective
                      Deferral Provisions for Members of the Ameren Leadership
                      Team as amended and restated effective January 1, 2001
                      (2000 Form 10-K, Exhibit 10.2).

         10.6         Asset Transfer Agreement between Generating Company and
                      AmerenCIPS (June 30, 2000 AmerenCIPS Form 10-Q, Exhibit
                      10).

         10.7         Amended Electric Power Supply Agreement between Generating
                      Company and AmerenEnergy Marketing Company (Marketing Co.)
                      (File No. 333-56594, Exhibit 10.2).

         10.8         2nd Amended Electric Power Supply Agreement between
                      Generating Company and Marketing Co. (March 31, 2001 Form
                      10-Q, Exhibit 10.1).

         10.9         Electric Power Supply Agreement between Marketing Co. and
                      AmerenCIPS (File No. 333-56594, Exhibit 10.3).


                                       5


      EXHIBIT NO.                            DESCRIPTION

         10.10        Amended Electric Power Supply Agreement between Marketing
                      Co. and AmerenCIPS (March 31, 2001 Form 10-Q, Exhibit
                      10.2).

         10.11        Power Sales Agreement between Marketing Co. and AmerenUE
                      (September 30, 2001 Generating Company Form 10-Q, Exhibit
                      10.1).

         10.12        Power Sales Agreement between Marketing Co. and AmerenUE
                      (March 31, 2002 Generating Company Form 10-Q, Exhibit
                      10.1).

         10.13        Amended Joint Dispatch Agreement among Generating Company,
                      AmerenCIPS and AmerenUE (File No. 333-56594, Exhibit
                      10.4).

         10.14        Lease Agreement dated as of December 1, 2002 between the
                      City of Bowling Green, Missouri, as Lessor, and AmerenUE,
                      as Lessee (AmerenUE 2002 Form 10-K, Exhibit 10.9).

         10.15        Trust Indenture dated as of December 1, 2002 between the
                      City of Bowling Green, Missouri and Commerce Bank, N.A. as
                      Trustee (AmerenUE 2002 Form 10-K, Exhibit 10.10).

         10.16        Bond Purchase Agreement dated as of December 20, 2002
                      between the City of Bowling Green, Missouri and AmerenUE
                      as purchaser (AmerenUE 2002 Form 10-K, Exhibit 10.11).

         10.17        Amended and Restated Appendix I ITC Agreement dated
                      February 14, 2003 between the Midwest Independent
                      Transmission System Operator, Inc. (Midwest ISO) and
                      GridAmerica LLC (GridAmerica) (2002 Form 10-K, Exhibit
                      10.17).

         10.18        Amended and Restated Limited Liability Company Agreement
                      of GridAmerica dated February 14, 2003 (2002 Form 10-K,
                      Exhibit 10.18)

         10.19        Amended and Restated Master Agreement by and among
                      GridAmerica, GridAmerica Holdings Inc., GridAmerica
                      Companies and National Grid USA dated February 14, 2003
                      (2002 Form 10-K, Exhibit 10.19).

         10.20        Amended and Restated Operation Agreement by and among
                      AmerenUE, AmerenCIPS, American Transmission Systems, Inc.,
                      Northern Indiana Public Service Company and GridAmerica
                      dated February 14, 2003 (2002 Form 10-K, Exhibit 10.20).

         10.21     *  CILCO Executive Deferral Plan. As amended effective August
                      15, 1999 (CILCORP 1999 Form 10-K, Exhibit 10).

         10.22     *  CILCO Executive Deferral Plan II. As amended effective
                      April 1, 1999 (CILCORP 1999 Form 10-K, Exhibit 10a).

         10.23     *  CILCO Benefit Replacement Plan. As amended effective
                      August 15, 1999 (CILCORP 1999 Form 10-K, Exhibit 10b).

         10.24     *  Retention Agreement between Central Illinois Light Company
                      (CILCO) and Scott A. Cisel dated October 16, 2001 (CILCORP
                      2001 Form 10-K, Exhibit 10c).

         10.25     *  Bonus Agreements dated January 21, 2003, between CILCO and
                      Robert J. Sprowls, Scott A. Cisel, James L. Luckey, III,
                      and Thomas S. Romanowski (CILCORP 2002 Form 10-K, Exhibit
                      10d).

         10.26     *  CILCO Involuntary Severance Pay Plan effective July 16,
                      2001 (CILCORP 2001 Form 10-K, Exhibit 10e).

         10.27     *  CILCO Restructured Executive Deferral Plan (approved
                      August 15, 1999) (CILCORP 1999 Form 10-K, Exhibit 10e).


                                       6


         EXHIBIT NO.              DESCRIPTION

         12.1         Statement of Computation of Ratio of Earnings to Fixed
                      Charges and Preferred Stock Dividend Requirements (2002
                      Form 10-K, Exhibit 12.1).

         13.1     **  Those pages of the 2002 Annual Report incorporated herein
                      by reference.

         21.1         Subsidiaries of Ameren (2002 Form 10-K, Exhibit 21.1).

         23.1         Consent of Independent Accountants (2002 Form 10-K,
                      Exhibit 23.1).

         24.1         Power of Attorney (2002 Form 10-K, Exhibit 24.1).

         99.1         Stipulation and Agreement dated July 15, 2002 in Missouri
                      Public Service Commission (as No. EC-2002-1 (earnings
                      complaint case against AmerenUE) File Nos. 333-87506 and
                      333-87506-01, Exhibit 99.1).

         99.2         Certificate of Chief Executive Officer required by Section
                      906 of the Sarbanes-Oxley Act of 2002 (2002 Form 10-K,
                      Exhibit 99.2).

         99.3         Certificate of Chief Financial Officer required by Section
                      906 of the Sarbanes-Oxley Act of 2002 (2002 Form 10-K,
                      Exhibit 99.3).

         ----------------------------
         *  Management compensatory plan or arrangement.

         ** Filed herewith.


         EXHIBITS AVAILABLE UPON REQUEST

         The following instruments defining the rights of holders of certain
         unregistered long-term debt of AmerenCIPS and AmerenUE have not been
         filed with the SEC but will be furnished upon request.

                    Loan Agreement dated January 1, 1993, between AmerenCIPS and
                    Illinois Development Finance Authority (IDFA) in connection
                    with IDFA's $35,000,000, 6-3/8% Pollution Control Revenue
                    Refunding Bonds (Central Illinois Public Service Company
                    Project) 1993 Series A, due January 1, 2028.

                    Loan Agreement dated June 1, 1993, between AmerenCIPS and
                    IDFA in connection with IDFA's $17,500,000 Pollution Control
                    Revenue Refunding Bonds, 1993 Series B-1 due June 1, 2028
                    and $17,500,000 Pollution Control Revenue Refunding Bonds,
                    1993 Series B-2 due June 1, 2028.

                    Loan Agreement dated August 15, 1993, between AmerenCIPS and
                    IDFA in connection with IDFA's $35,000,000 Pollution Control
                    Revenue Refunding Bonds, 1993 Series C-1 due August 15, 2026
                    and $25,000,000 Pollution Control Revenue Refunding Bonds,
                    1993 Series C-2 due August 15, 2026.

                    Loan Agreement dated March 1, 2000, between AmerenCIPS and
                    IDFA in connection with the IDFA's $51,100,000 Pollution
                    Control Revenue Refunding Bonds (AmerenCIPS Project) Series
                    2000A due March 1, 2014.

                    Loan Agreement dated March 1, 2000, between AmerenUE and the
                    State Environmental Improvement and Energy Resources
                    Authority of the State of Missouri (EIERA) in connection
                    with the EIERA's $186,500,000 Environmental Improvement
                    Revenue Refunding Bonds (AmerenUE Project) ($63,500,000
                    Series 2000A, $63,000,000 Series 2000B, and $60,000,000
                    Series 2000C) due March 1, 2035.

Note:    Reports of Union Electric Company on Forms 8-K, 10-Q and 10-K are on
         file with the SEC under File Number 1-2967.

         Reports of Central Illinois Public Service Company on Forms 8-K, 10-Q
         and 10-K are on file with the SEC under File Number 1-3672.


                                       7

         Reports of AmerenEnergy Generating Company on Forms 8-K, 10-Q and 10-K
         are on file with the SEC under File Number 333-56594.

         Reports of CILCORP Inc. on Forms 8-K, 10-Q and 10-K are on file with
         the SEC under File Number 1-8946.

         Reports of Central Illinois Light Company on Forms 8-K, 10-Q and 10-K
         are on file with the SEC under File Number 1-2732.



                                   SIGNATURES

     Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized.

                                             AMEREN CORPORATION
                                                 (Registrant)

Date       April 1, 2003                     By    /s/ MARTIN J. LYONS
       -----------------------                   -------------------------------
                                                        Martin J. Lyons
                                                  Vice President and Controller
                                                 (Principal Accounting Officer)


                                 CERTIFICATIONS



         I, Charles W. Mueller, certify that:



         1.   I have reviewed this annual report on Form 10-K/A of Ameren
              Corporation;

         2.   Based on my knowledge, this annual report does not contain any
              untrue statement of a material fact or omit to state a material
              fact necessary to make the statements made, in light of the
              circumstances under which such statements were made, not
              misleading with respect to the period covered by this annual
              report;

         3.   Based on my knowledge, the financial statements, and other
              financial information included in this annual report, fairly
              present in all material respects the financial condition, results
              of operations and cash flows of the registrant as of, and for, the
              periods presented in this annual report;

         4.   The registrant's other certifying officer and I are responsible
              for establishing and maintaining disclosure controls and
              procedures (as defined in Exchange Act Rules 13a-14 and 15d-14)
              for the registrant and have:

              a)  designed such disclosure controls and procedures to ensure
                  that material information relating to the registrant,
                  including its consolidated subsidiaries, is made known to us
                  by others within those entities, particularly during the
                  period in which this annual report is being prepared;

              b)  evaluated the effectiveness of the registrant's disclosure
                  controls and procedures as of a date within 90 days prior to
                  the filing date of this annual report (the Evaluation Date);
                  and

              c)  presented in this annual report our conclusions about the
                  effectiveness of the disclosure controls and procedures based
                  on our evaluation as of the Evaluation Date;

         5.   The registrant's other certifying officer and I have disclosed,
              based on our most recent evaluation, to the registrant's auditors
              and the audit committee of registrant's board of directors (or
              persons performing the equivalent functions):

              a)  all significant deficiencies in the design or operation of
                  internal controls which could adversely affect the
                  registrant's ability to record, process, summarize and report
                  financial data and have identified for the registrant's
                  auditors any material weaknesses in internal controls; and

              b)  any fraud, whether or not material, that involves management
                  or other employees who have a significant role in the
                  registrant's internal controls; and


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                           CERTIFICATIONS (CONTINUED)


         6.   The registrant's other certifying officer and I have indicated in
              this annual report whether there were significant changes in
              internal controls or in other factors that could significantly
              affect internal controls subsequent to the date of our most recent
              evaluation, including any corrective actions with regard to
              significant deficiencies and material weaknesses.



Date:  April 1, 2003                          /s/ Charles W. Mueller
                                              ----------------------------------
                                              Charles W. Mueller
                                              Chief Executive Officer


         I, Warner L. Baxter, certify that:



         1.   I have reviewed this annual report on Form 10-K/A of Ameren
              Corporation;

         2.   Based on my knowledge, this annual report does not contain any
              untrue statement of a material fact or omit to state a material
              fact necessary to make the statements made, in light of the
              circumstances under which such statements were made, not
              misleading with respect to the period covered by this annual
              report;

         3.   Based on my knowledge, the financial statements, and other
              financial information included in this annual report, fairly
              present in all material respects the financial condition, results
              of operations and cash flows of the registrant as of, and for, the
              periods presented in this annual report;

         4.   The registrant's other certifying officer and I are responsible
              for establishing and maintaining disclosure controls and
              procedures (as defined in Exchange Act Rules 13a-14 and 15d-14)
              for the registrant and have:

              a)  designed such disclosure controls and procedures to ensure
                  that material information relating to the registrant,
                  including its consolidated subsidiaries, is made known to us
                  by others within those entities, particularly during the
                  period in which this annual report is being prepared;

              b)  evaluated the effectiveness of the registrant's disclosure
                  controls and procedures as of a date within 90 days prior to
                  the filing date of this annual report (the Evaluation Date);
                  and

              c)  presented in this annual report our conclusions about the
                  effectiveness of the disclosure controls and procedures based
                  on our evaluation as of the Evaluation Date;

         5.   The registrant's other certifying officer and I have disclosed,
              based on our most recent evaluation, to the registrant's auditors
              and the audit committee of registrant's board of directors (or
              persons performing the equivalent functions):

              a)  all significant deficiencies in the design or operation of
                  internal controls which could adversely affect the
                  registrant's ability to record, process, summarize and report
                  financial data and have identified for the registrant's
                  auditors any material weaknesses in internal controls; and

              b)  any fraud, whether or not material, that involves management
                  or other employees who have a significant role in the
                  registrant's internal controls; and

         6.   The registrant's other certifying officer and I have indicated in
              this annual report whether there were significant changes in
              internal controls or in other factors that could significantly
              affect internal


                                       9


                           CERTIFICATIONS (CONTINUED)


         controls subsequent to the date of our most recent evaluation,
         including any corrective actions with regard to significant
         deficiencies and material weaknesses.



Date:  April 1, 2003                         /s/ Warner L. Baxter
                                            ------------------------------------
                                            Warner L. Baxter
                                            Chief Financial Officer



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