UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 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 14, 2004



<TABLE>
<CAPTION>


                 Exact Name of Registrant as specified in its charter;
Commission       State of Incorporation;                                           IRS Employer
File Number      Address and Telephone Number                                      Identification No.
-----------      ----------------------------                                      ------------------
<S>             <C>                                                                   <C>
1-14756          Ameren Corporation                                                    43-1723446
                 (Missouri Corporation)
                 1901 Chouteau Avenue
                 St. Louis, Missouri 63103 (314) 621-3222

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

</TABLE>

     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))


<PAGE>


SECTION 8 - OTHER EVENTS
Item 8.01 Other Events.

On October 14, 2004, Illinois Power Company ("Illinois  Power"),  doing business
as AmerenIP and a subsidiary of Ameren Corporation  ("Ameren"),  unconditionally
called for  redemption on November 15, 2004,  $192,500,000  aggregate  principal
amount of its Mortgage Bonds,  11.50% Series due 2010 (the "Bonds").  On October
15, 2004,  Illinois  Power offered to purchase for cash any and all of its Bonds
that are not redeemed ($357,500,000 aggregate principal amount).

For additional information, reference is made to the press release dated October
15, 2004, which is included as Exhibit 99.1 and incorporated by reference
herein.



SECTION 9 - Financial Statements and EXHIBITS
Item 9.01 Financial Statements and Exhibits.


(a) Not applicable

(b) Not applicable

(c) Exhibits. The following exhibit is included with this Report:

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

       99.1           Press release regarding Illinois Power's redemption of and
                      tender offer for the Bonds, dated October 15, 2004.


     This  combined  Form 8-K is being filed  separately  by Ameren and Illinois
Power (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.



                                      -2-

<PAGE>



                                    SIGNATURE



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)


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


                                    ILLINOIS POWER COMPANY
                                    (Registrant)



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





Date:  October 20, 2004





                                      -3-

<PAGE>



                                  Exhibit Index
                                  -------------

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

99.1                - Press release regarding Illinois Power's redemption of and
                      tender offer for the Bonds, dated October 15, 2004.
[{"type": "8-K", "sequence": "1", "filename": "amc8-k102004.txt", "description": "AMC AND IP 8-K DATED 10/20/04", "secsgml_size_bytes": 5226}]
[{"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": "041087116"}, "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": "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": "041087115"}, "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, DC 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 14, 2004
Exact Name of Registrant as specified in its charter;
Commission       State of Incorporation;                                           IRS Employer
File Number      Address and Telephone Number                                      Identification No.
-----------      ----------------------------                                      ------------------
1-14756          Ameren Corporation                                                    43-1723446
                 (Missouri Corporation)
                 1901 Chouteau Avenue
                 St. Louis, Missouri 63103 (314) 621-3222

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))
SECTION 8 - OTHER EVENTS
Item 8.01 Other Events.

On October 14, 2004, Illinois Power Company ("Illinois  Power"),  doing business
as AmerenIP and a subsidiary of Ameren Corporation  ("Ameren"),  unconditionally
called for  redemption on November 15, 2004,  $192,500,000  aggregate  principal
amount of its Mortgage Bonds,  11.50% Series due 2010 (the "Bonds").  On October
15, 2004,  Illinois  Power offered to purchase for cash any and all of its Bonds
that are not redeemed ($357,500,000 aggregate principal amount).

For additional information, reference is made to the press release dated October
15, 2004, which is included as Exhibit 99.1 and incorporated by reference
herein.

SECTION 9 - Financial Statements and EXHIBITS
Item 9.01 Financial Statements and Exhibits.

(a) Not applicable

(b) Not applicable

(c) Exhibits. The following exhibit is included with this Report:

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

       99.1           Press release regarding Illinois Power's redemption of and
                      tender offer for the Bonds, dated October 15, 2004.

     This  combined  Form 8-K is being filed  separately  by Ameren and Illinois
Power (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.

                                      -2-
SIGNATURE

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)

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

                                    ILLINOIS POWER COMPANY
                                    (Registrant)

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

Date:  October 20, 2004

                                      -3-
Exhibit Index
                                  -------------

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

99.1                - Press release regarding Illinois Power's redemption of and
                      tender offer for the Bonds, dated October 15, 2004.