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

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

                                    FORM 8-K

                                 CURRENT REPORT
                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934

                Date of report (Date of earliest event reported):



                                 October 8, 2004


<TABLE>
<CAPTION>

                                         Exact Name of Registrant as
                                         Specified in Charter;
                                         State of Incorporation;                IRS Employer
 Commission File Number                  Address and Telephone Number           Identification Number
 ----------------------                  ----------------------------           ---------------------
<S>                                       <C>                                   <C>
1-14756                                  Ameren Corporation                     43-1723446
                                         (Missouri Corporation)
                                         1901 Chouteau Avenue
                                         St. Louis, MO 63103
                                         (314) 621-3222

1-3672                                   Central Illinois Public Service        37-0211380
                                         Company
                                         (Illinois Corporation)
                                         607 East Adams Street
                                         Springfield, Illinois 62739
                                         (217) 523-3600

1-2732                                   Central Illinois Light Company         37-0211050
                                         (Illinois Corporation)
                                         300 Liberty Street
                                         Peoria, Illinois 61602
                                         (309) 677-5230

1-3004                                   Illinois Power Company                 37-0344645
                                         (Illinois Corporation)
                                         500 South 27th Street
                                         Decatur, Illinois 62521
                                         (217) 424-6600

</TABLE>

<PAGE>


Check  the  appropriate  box  below  if the  Form  8-K  filing  is  intended  to
simultaneously  satisfy the filing obligation of the registrant under any of the
following provisions:

     [ ] Written  communications  pursuant to Rule 425 under the  Securities Act
(17 CFR 230.425)

     [ ] Soliciting  material pursuant to Rule 14a-12 under the Exchange Act (17
CFR 240.14a-12)

     [ ]  Pre-commencement  communications  pursuant to Rule 14d-2(b)  under the
Exchange Act (17 CFR 240.14d-2(b))

     [ ]  Pre-commencement  communications  pursuant to Rule 13e-4(c)  under the
Exchange Act (17 CFR 240.13e-4(c))


                                      -2-
<PAGE>


SECTION 5 - CORPORATE GOVERNANCE AND MANAGEMENT

ITEM 5.02 Departure of Directors or Principal  Officers;  Election of Directors;
Appointment of Principal Officers.

     On October 8, 2004,  Ameren  Corporation  ("Ameren")  announced among other
subsidiary  level  organization  changes  the  election  of  Scott  A.  Cisel as
President of its Illinois-based  utility  subsidiaries,  Central Illinois Public
Service Company ("CIPS"),  Central Illinois Light Company ("CILCO") and Illinois
Power Company ("IPC") to replace Gary L. Rainwater  effective  October 15, 2004.
Mr. Cisel will serve as the principal  operating  officer of these companies and
Mr. Rainwater will continue as principal  executive officer of each company.  In
conjunction with his election as President, Mr. Cisel was also elected to fill a
vacancy on the Board of Directors of CIPS and IPC effective October 15, 2004. He
is already a member of CILCO's Board of Directors.

     Mr.  Cisel,  age 51,  assumed  the  position  of Vice  President  of IPC in
September 2004 upon Ameren's acquisition of IPC. He assumed the position of Vice
President and Chief  Operating  Officer for CILCO upon Ameren's  acquisition  of
CILCO in January 2003 after serving as Senior Vice President. Prior to that, Mr.
Cisel had held various management positions at CILCO in sales, customer services
and  district  operations,  including  service as manager of  Commercial  Office
Operations in 1981,  manager of Consumer and Energy Services in 1984, manager of
Rates,  Sales and Customer Service in 1988,  director of Corporate Sales in 1993
and from 1995 to 2001, at first managing Sales and Marketing,  then  Legislative
and Public Affairs and later Sales, Marketing and Trading. In April 2001, he was
named Senior Vice President of CILCO.

ITEM 5.03 Amendments to Articles of  Incorporation  or Bylaws;  Change in Fiscal
Year.

     On  October  8, 2004,  the  Bylaws of CIPS,  CILCO and IPC were  amended by
action by unanimous  written  consent of the Board of Directors of each of these
companies as follows:

     o    The  position  of Chief  Operating  Officer  was added as a  principal
          officer of these  companies  which may be  elected by their  Boards of
          Directors.

     o    With  respect to CIPS' and  CILCO's  Bylaws,  the size of the Board of
          Directors  was  changed  to  not  less  than  3 and  not  more  than 8
          directors.

     o    With  respect  to  CIPS'  and  IPC's  Bylaws,  the  principal  officer
          positions  were  revised  to  permit a  separate  President  and Chief
          Executive Officer.

     o    With  respect to CIPS'  Bylaws,  the position of Chairman of the Board
          was added as a principal  officer which may be elected by the Board of
          Directors.

For additional  information,  reference is made to the Bylaws of CIPS, CILCO and
IPC, as amended  October 8, 2004,  which are  included as Exhibits  3.1, 3.2 and
3.3, respectively, hereto and incorporated by reference herein.


SECTION 9 - FINANCIAL STATEMENTS AND EXHIBITS

Item 9.01 Financial Statements and Exhibits.

(c)    Exhibits


<TABLE>
<CAPTION>
             <S>                   <C>
         ----------------------------------------------------------------------------------------------
         |  3.1            |  Bylaws of Central Illinois Public Service Company as amended            |
         |                 |  October 8, 2004.                                                        |
         |--------------------------------------------------------------------------------------------|
         |  3.2            |  Bylaws of Central Illinois Light Company as amended October 8, 2004.    |
         |--------------------------------------------------------------------------------------------|
         |  3.3            |  Bylaws of Illinois Power Company as amended October 8, 2004             |
         ----------------------------------------------------------------------------------------------
</TABLE>


     This combined Form 8-K is being filed separately by Ameren, CIPS, CILCO and
IPC  (each  a  "registrant").  Information  contained  herein  relating  to  any
individual  registrant has been filed by such  registrant on its own behalf.  No
registrant  makes any  representation  as to  information  relating to any other
registrant.

                                      -3-
<PAGE>


                                   SIGNATURES



Pursuant  to the  requirements  of the  Securities  Exchange  Act of 1934,  each
registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned  thereunto  duly  authorized.  The  signature  for each  undersigned
company  shall be deemed to relate  only to  matters  having  reference  to such
company or its subsidiaries.

                                       AMEREN CORPORATION
                                       (Registrant)


                                         /s/ Martin J. Lyons
                                       ----------------------------------------
                                       Martin J. Lyons
                                       Vice President and Controller
                                       (Principal Accounting Officer)


                                       CENTRAL ILLINOIS PUBLIC SERVICE COMPANY
                                       (Registrant)


                                         /s/ Martin J. Lyons
                                       ----------------------------------------
                                       Martin J. Lyons
                                       Vice President and Controller
                                       (Principal Accounting Officer)


                                       CENTRAL ILLINOIS LIGHT COMPANY
                                       (Registrant)


                                         /s/ Martin J. Lyons
                                       ----------------------------------------
                                       Martin J. Lyons
                                       Vice President and Controller
                                       (Principal Accounting Officer)


                                       ILLINOIS POWER COMPANY
                                       (Registrant)


                                         /s/ Martin J. Lyons
                                       ----------------------------------------
                                       Martin J. Lyons
                                       Vice President and Controller
                                       (Principal Accounting Officer)





Date: October 14, 2004




                                      -4-
[{"type": "8-K", "sequence": "1", "filename": "ameren8k101404.txt", "description": "AMEREN8K 10-14-2004", "secsgml_size_bytes": 9887}]
[{"company-data": {"conformed-name": "ILLINOIS POWER CO", "cik": "0000049816", "assigned-sic": "4931", "irs-number": "370344645", "state-of-incorporation": "IL", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-03004", "film-number": "041078201"}, "business-address": {"street1": "500 S 27TH ST", "street2": "C/O HARRIS TRUST & SAVINGS BANK", "city": "DECATUR", "state": "IL", "zip": "62525-1805", "phone": "2174246600"}, "mail-address": {"street1": "500 SOUTH 27TH STREET", "city": "DECATUR", "state": "IL", "zip": "62521"}, "former-company": {"former-conformed-name": "ILLINOIS IOWA POWER CO", "date-changed": "19660822"}}, {"company-data": {"conformed-name": "CENTRAL ILLINOIS PUBLIC SERVICE CO", "cik": "0000018654", "assigned-sic": "4931", "irs-number": "370211380", "state-of-incorporation": "IL", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-03672", "film-number": "041078203"}, "business-address": {"street1": "607 E ADAMS ST", "city": "SPRINGFIELD", "state": "IL", "zip": "62739", "phone": "217-523-3600"}, "mail-address": {"street1": "CENTRAL ILLINOIS PUBLIC SERVICE CO", "street2": "607 E ADAMS ST", "city": "SPRINGFIELD", "state": "IL", "zip": "62739"}}, {"company-data": {"conformed-name": "CENTRAL ILLINOIS LIGHT CO", "cik": "0000018651", "assigned-sic": "4931", "irs-number": "370211050", "state-of-incorporation": "IL", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-02732", "film-number": "041078202"}, "business-address": {"street1": "300 LIBERTY ST", "city": "PEORIA", "state": "IL", "zip": "61602", "phone": "309-677-5230"}, "mail-address": {"street1": "300 LIBERTY STREET", "city": "PEORIA", "state": "IL", "zip": "61602"}}, {"company-data": {"conformed-name": "AMEREN CORP", "cik": "0001002910", "assigned-sic": "4931", "irs-number": "431723446", "state-of-incorporation": "MO", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-14756", "film-number": "041078200"}, "business-address": {"street1": "1901 CHOUTEAU AVE", "street2": "MC 1370", "city": "ST LOUIS", "state": "MO", "zip": "63166-6149", "phone": "314-621-3222"}, "mail-address": {"street1": "1901 CHOUTEAU AVE", "street2": "MC 1370", "city": "ST LOUIS", "state": "MO", "zip": "63103"}}]
UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                    FORM 8-K

                                 CURRENT REPORT
                     Pursuant to Section 13 or 15(d) of the
                         Securities Exchange Act of 1934

                Date of report (Date of earliest event reported):

                                 October 8, 2004
Exact Name of Registrant as
                                         Specified in Charter;
                                         State of Incorporation;                IRS Employer
 Commission File Number                  Address and Telephone Number           Identification Number
 ----------------------                  ----------------------------           ---------------------
1-14756                                  Ameren Corporation                     43-1723446
                                         (Missouri Corporation)
                                         1901 Chouteau Avenue
                                         St. Louis, MO 63103
                                         (314) 621-3222

1-3672                                   Central Illinois Public Service        37-0211380
                                         Company
                                         (Illinois Corporation)
                                         607 East Adams Street
                                         Springfield, Illinois 62739
                                         (217) 523-3600

1-2732                                   Central Illinois Light Company         37-0211050
                                         (Illinois Corporation)
                                         300 Liberty Street
                                         Peoria, Illinois 61602
                                         (309) 677-5230

1-3004                                   Illinois Power Company                 37-0344645
                                         (Illinois Corporation)
                                         500 South 27th Street
                                         Decatur, Illinois 62521
                                         (217) 424-6600
Check  the  appropriate  box  below  if the  Form  8-K  filing  is  intended  to
simultaneously  satisfy the filing obligation of the registrant under any of the
following provisions:

     [ ] Written  communications  pursuant to Rule 425 under the  Securities Act
(17 CFR 230.425)

     [ ] Soliciting  material pursuant to Rule 14a-12 under the Exchange Act (17
CFR 240.14a-12)

     [ ]  Pre-commencement  communications  pursuant to Rule 14d-2(b)  under the
Exchange Act (17 CFR 240.14d-2(b))

     [ ]  Pre-commencement  communications  pursuant to Rule 13e-4(c)  under the
Exchange Act (17 CFR 240.13e-4(c))

                                      -2-
SECTION 5 - CORPORATE GOVERNANCE AND MANAGEMENT

ITEM 5.02 Departure of Directors or Principal  Officers;  Election of Directors;
Appointment of Principal Officers.

     On October 8, 2004,  Ameren  Corporation  ("Ameren")  announced among other
subsidiary  level  organization  changes  the  election  of  Scott  A.  Cisel as
President of its Illinois-based  utility  subsidiaries,  Central Illinois Public
Service Company ("CIPS"),  Central Illinois Light Company ("CILCO") and Illinois
Power Company ("IPC") to replace Gary L. Rainwater  effective  October 15, 2004.
Mr. Cisel will serve as the principal  operating  officer of these companies and
Mr. Rainwater will continue as principal  executive officer of each company.  In
conjunction with his election as President, Mr. Cisel was also elected to fill a
vacancy on the Board of Directors of CIPS and IPC effective October 15, 2004. He
is already a member of CILCO's Board of Directors.

     Mr.  Cisel,  age 51,  assumed  the  position  of Vice  President  of IPC in
September 2004 upon Ameren's acquisition of IPC. He assumed the position of Vice
President and Chief  Operating  Officer for CILCO upon Ameren's  acquisition  of
CILCO in January 2003 after serving as Senior Vice President. Prior to that, Mr.
Cisel had held various management positions at CILCO in sales, customer services
and  district  operations,  including  service as manager of  Commercial  Office
Operations in 1981,  manager of Consumer and Energy Services in 1984, manager of
Rates,  Sales and Customer Service in 1988,  director of Corporate Sales in 1993
and from 1995 to 2001, at first managing Sales and Marketing,  then  Legislative
and Public Affairs and later Sales, Marketing and Trading. In April 2001, he was
named Senior Vice President of CILCO.

ITEM 5.03 Amendments to Articles of  Incorporation  or Bylaws;  Change in Fiscal
Year.

     On  October  8, 2004,  the  Bylaws of CIPS,  CILCO and IPC were  amended by
action by unanimous  written  consent of the Board of Directors of each of these
companies as follows:

     o    The  position  of Chief  Operating  Officer  was added as a  principal
          officer of these  companies  which may be  elected by their  Boards of
          Directors.

     o    With  respect to CIPS' and  CILCO's  Bylaws,  the size of the Board of
          Directors  was  changed  to  not  less  than  3 and  not  more  than 8
          directors.

     o    With  respect  to  CIPS'  and  IPC's  Bylaws,  the  principal  officer
          positions  were  revised  to  permit a  separate  President  and Chief
          Executive Officer.

     o    With  respect to CIPS'  Bylaws,  the position of Chairman of the Board
          was added as a principal  officer which may be elected by the Board of
          Directors.

For additional  information,  reference is made to the Bylaws of CIPS, CILCO and
IPC, as amended  October 8, 2004,  which are  included as Exhibits  3.1, 3.2 and
3.3, respectively, hereto and incorporated by reference herein.

SECTION 9 - FINANCIAL STATEMENTS AND EXHIBITS

Item 9.01 Financial Statements and Exhibits.

(c)    Exhibits
----------------------------------------------------------------------------------------------
         |  3.1            |  Bylaws of Central Illinois Public Service Company as amended            |
         |                 |  October 8, 2004.                                                        |
         |--------------------------------------------------------------------------------------------|
         |  3.2            |  Bylaws of Central Illinois Light Company as amended October 8, 2004.    |
         |--------------------------------------------------------------------------------------------|
         |  3.3            |  Bylaws of Illinois Power Company as amended October 8, 2004             |
         ----------------------------------------------------------------------------------------------
This combined Form 8-K is being filed separately by Ameren, CIPS, CILCO and
IPC  (each  a  "registrant").  Information  contained  herein  relating  to  any
individual  registrant has been filed by such  registrant on its own behalf.  No
registrant  makes any  representation  as to  information  relating to any other
registrant.

                                      -3-
SIGNATURES

Pursuant  to the  requirements  of the  Securities  Exchange  Act of 1934,  each
registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned  thereunto  duly  authorized.  The  signature  for each  undersigned
company  shall be deemed to relate  only to  matters  having  reference  to such
company or its subsidiaries.

                                       AMEREN CORPORATION
                                       (Registrant)

                                         /s/ Martin J. Lyons
                                       ----------------------------------------
                                       Martin J. Lyons
                                       Vice President and Controller
                                       (Principal Accounting Officer)

                                       CENTRAL ILLINOIS PUBLIC SERVICE COMPANY
                                       (Registrant)

                                         /s/ Martin J. Lyons
                                       ----------------------------------------
                                       Martin J. Lyons
                                       Vice President and Controller
                                       (Principal Accounting Officer)

                                       CENTRAL ILLINOIS LIGHT COMPANY
                                       (Registrant)

                                         /s/ Martin J. Lyons
                                       ----------------------------------------
                                       Martin J. Lyons
                                       Vice President and Controller
                                       (Principal Accounting Officer)

                                       ILLINOIS POWER COMPANY
                                       (Registrant)

                                         /s/ Martin J. Lyons
                                       ----------------------------------------
                                       Martin J. Lyons
                                       Vice President and Controller
                                       (Principal Accounting Officer)

Date: October 14, 2004

                                      -4-