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 1-3672

                     CENTRAL ILLINOIS PUBLIC SERVICE COMPANY
             (Exact name of registrant as specified in its charter)

         Illinois                                       37-0211380
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
incorporation or organization)

               607 East Adams Street, Springfield, Illinois 62739
              (Address of principal executive offices and Zip Code)

       Registrant's telephone number, including area code: (217) 523-3600

        Securities Registered Pursuant to Section 12(b) of the Act: None.

           Securities Registered Pursuant to Section 12(g) of the Act:
                                 Title Of Class

              Cumulative Preferred Stock, par value $100 per share

           Depositary Shares, each representing one-fourth of a share
         of 6.625% Cumulative Preferred Stock, par value $100 per share

     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. (X).

     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 ( ). No (X).

     As of June 28, 2002,  Ameren  Corporation  held all 25,452,373  outstanding
shares of common stock,  without par value,  of Central  Illinois Public Service
Company.  The  aggregate  market  value of the  voting  preferred  stock held by
non-affiliates  of Central  Illinois  Public  Service  Company at June 28, 2002,
determined by trader derived  valuations based on current market conditions on a
spread  basis  (excluding  preferred  stock for which  prices  are not  publicly
available) was $28,200,000.

     Shares of Common Stock without par value, outstanding as of March 21, 2003:
25,452,373 shares (all owned by Ameren Corporation).

                     Documents incorporated by references.

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

<PAGE>


                                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  12.2  Statement  of
Computations  of Ratio of Earnings to Fixed Charges and Preferred Stock Dividend
Requirements 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
     -----------                       -----------

      3.1(i)        Restated  Articles  of  Incorporation  of  Central  Illinois
                    Public Service Company d/b/a AmerenCIPS  (AmerenCIPS) (March
                    31, 1994 Form 10-Q, Exhibit 3(b)).


      3.2(ii)       By-Laws of AmerenCIPS as amended  effective January 21, 2003
                    (2002 Form 10-K, Exhibit 3.2(ii)).

      4.1           Indenture  of  Mortgage  or Deed of Trust  dated  October 1,
                    1941, from 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).

      4.2           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 4.1
                    (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;  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 Form 8-K dated May
                    15,  1992;  Exhibit  4.02 to Form 8-K  dated  July 1,  1992;
                    Exhibit 4.02 to Form 8-K dated  September 15, 1992;  Exhibit
                    4.02 to Form 8-K dated March 30, 1993;  Exhibit 4.03 to Form
                    8-K dated June 5, 1995; Exhibit 4.03 to Form 8-K dated March
                    15,  1997;  Exhibit  4.03 to Form 8-K  dated  June 1,  1997;
                    Exhibit 4.2, in File No. 333-59438;  and Exhibit 4.1 to June
                    30, 2001 Form 10-Q.)

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

      10.1        * Form of Director's  Retirement  Income Plan (1990 Form 10-K,
                    Exhibit 10.04).

      10.2        * Form of Excess Benefit Plan (1994 Form 10-K, Exhibit 10.10).

                                       2

<PAGE>

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

      10.3        * Amendment  to  Form of Excess  Benefit Plan (1995 Form 10-K,
                    Exhibit 10.07).

      10.4        * Form of Special  Executive  Retirement Plan (1994 Form 10-K,
                    Exhibit 10.11).

      10.5        * Amendment to Form of Special Executive Retirement Plan (1995
                    Form 10-K, Exhibit 10.09).

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

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

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

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

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

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

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

      10.13         2nd  Amended   Electric  Power  Supply   Agreement   between
                    Generating  Company and Marketing Co. (Ameren March 31, 2001
                    Form 10-Q, Exhibit 10.1).

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

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

      10.16         Amended Joint Dispatch  Agreement among Generating  Company,
                    AmerenCIPS  and  Union   Electric   Company  d/b/a  AmerenUE
                    (AmerenUE) (File No. 333-56594, Exhibit 10.4).

      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) (Ameren 2002 Form 10-K, Exhibit 10.17).

      10.18         Amended and Restated Limited  Liability Company Agreement of
                    GridAmerica  dated February 14, 2003 (Ameren 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
                    (Ameren 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  (Ameren  2002 Form 10-K,  Exhibit
                    10.20).

      12.2       ** Statement  of  Computations  of Ratio of  Earnings  to Fixed
                    Charges and Preferred Stock Dividend Requirements.

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

                                       3

<PAGE>



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

      99.1          Certificate of Chief Executive  Officer  required by Section
                    906 of the  Sarbanes-Oxley  Act of  2002  (2002  Form  10-K,
                    Exhibit 99.1).

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

    --------------------
    *    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 the Company 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.

Note:     Reports of Ameren  Corporation on Forms 8-K, 10-Q and 10-K are on file
          with the SEC under File Number 1-14756.

          Reports of AmerenUE  on Forms 8-K,  10-Q and 10-K are on file with the
          SEC under File Number 1-2967.

          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.


                                       4

<PAGE>


          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 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.

                                         CENTRAL ILLINOIS PUBLIC SERVICE COMPANY
                                                      (Registrant)


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

                                 CERTIFICATIONS



     I, Gary L. Rainwater, certify that:


     1.   I have reviewed this annual report on Form 10-K/A of Central  Illinois
Public Service Company;

     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

                                       5

<PAGE>

                           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/ GARY L. RAINWATER
                                          --------------------------------------
                                                     Gary L. Rainwater
                                                  Chief Executive Officer

     I, Warner L. Baxter, certify that:


     1.   I have reviewed this annual report on Form 10-K/A of Central  Illinois
Public Service Company;

     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 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

                                       6