Edgar Filing: AMEREN CORP

AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON FEBRUARY 13, 2004
REGISTRATION NO. 333-______
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SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM S-3

REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

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

STATE OF MISSOURI 43-1723446
(State or other jurisdiction (IRS Employer
of incorporation or organization) Identification No.)

1901 CHOUTEAU AVENUE
ST. LOUIS, MISSOURI 63103
(314) 621-3222
(Address, including zip code, and telephone number, including area code,
of registrant's principal executive offices)

WARNER L. BAXTER
EXECUTIVE VICE PRESIDENT AND CHIEF FINANCIAL OFFICER

STEVEN R. SULLIVAN
SENIOR VICE PRESIDENT GOVERNMENTAL/REGULATORY POLICY,
GENERAL COUNSEL AND SECRETARY
1901 CHOUTEAU AVENUE
ST. LOUIS, MISSOURI 63103
(314) 621-3222
(Names, address, including zip code, and telephone number,
including area code, of agents for service)

APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: From time
to time after the effective date of the registration statement as determined by
market conditions and other factors.

If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box. [ ]

If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or interest
reinvestment plans, check the following box. [X]

If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act of 1933, please check the
following box and list the Securities Act of 1933 registration statement number
of the earlier effective registration statement for the same offering. [ ]

If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act of 1933, check the following box and list the
Securities Act of 1933 registration statement number of the earlier effective
registration statement for the same offering. [ ]

If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. [ ]

CALCULATION OF REGISTRATION FEE
=============================================================================================
PROPOSED
PROPOSED MAXIMUM
TITLE OF EACH CLASS AMOUNT TO BE MAXIMUM AGGREGATE
OF SECURITIES TO BE REGISTERED OFFERING PRICE OFFERING AMOUNT OF
REGISTERED (1)(2) PER UNIT (2) PRICE (3) REGISTRATION FEE (4)
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Common Stock, 6,000,000 shares $46.33 $277,980,000 $35,221
$.01 par value
(including
associated
preferred share
purchase rights)
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(1) In addition, pursuant to Rule 416(a) of the Securities Act of 1933, this
registration statement also covers such indeterminable number of additional
securities as may become deliverable as a result of stock splits, stock
dividends or similar transactions, in accordance with the provisions of the
Plan.

(2) The preferred share purchase rights are attached to and will trade with the
common stock. The value attributable to the preferred share purchase
rights, if any, is reflected in the market price of the common stock.

(3) Estimated solely for purposes of calculating the registration fee pursuant
to Rule 457(c) under the Securities Act of 1933 on the basis of the average
of the high and low prices of the registrant's common stock on the New York
Stock Exchange composite tape on February 9, 2004.

(4) Since no separate consideration is paid for the preferred share purchase
rights, the registration fee for such securities is included in the fee for
the common stock.

Pursuant to Rule 429 under the Securities Act, the prospectus filed as part of
this registration statement will be used as a combined prospectus in connection
with this registration statement and Registration Statement No. 333-39400.

THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES
AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL FILE
A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT
SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF THE
SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(A),
MAY DETERMINE.
==============================================================================

SUBJECT TO COMPLETION, DATED FEBRUARY 13, 2004
PROSPECTUS
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[AMEREN LOGO]

DRPLUS

DIVIDEND REINVESTMENT AND STOCK PURCHASE PLAN

Ameren Corporation has established its DRPlus Dividend Reinvestment and
Stock Purchase Plan (Plan) to provide participants with a convenient way to
purchase shares of our common stock and to reinvest all or a portion of the cash
dividends paid on our common stock and the preferred stock of our subsidiaries
in additional shares of our common stock.

PARTICIPANTS IN THE PLAN MAY:

o Reinvest all or a portion of cash dividends paid on our common stock
and the preferred stock of our subsidiaries in additional shares of
common stock;

o Increase their investment in common stock by making optional cash
investments of at least $25 at any time;

o Make an initial investment in common stock with a cash investment of
at least $250;

o Receive, upon request, certificates for whole shares of common stock
credited to their Plan accounts;

o Deposit certificates representing common stock into their Plan
accounts for safekeeping; and

o Sell shares of common stock credited to their Plan accounts.

Shares of common stock purchased under the Plan will, at our option, be
newly issued shares or treasury shares purchased directly from us, or shares
purchased in the open market or in privately negotiated transactions. Any open
market or privately negotiated purchases will be made through an independent
agent selected by us. This prospectus relates to _________ shares of common
stock offered under the Plan.

If you are currently participating in the Plan, you will remain enrolled in
the Plan, and you do not have to take any action unless you wish to terminate
your participation or change your election in the Plan.

Our common stock is listed on the New York Stock Exchange under the ticker
symbol "AEE."

To the extent required by applicable law in certain jurisdictions, shares
of common stock offered under the Plan to certain persons are offered only
through a registered broker/dealer in such jurisdictions.

Our principal executive offices are located at 1901 Chouteau Avenue, St.
Louis, Missouri 63103 and our telephone number is (314) 621-3222.

Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if this
prospectus is truthful or complete. Any representation to the contrary is a
criminal offense.

THE DATE OF THIS PROSPECTUS IS .

--------------------------------------------------------------------------------
The information in this prospectus is not complete and may be changed. Ameren
Corporation may not sell these securities until the registration statement filed
with the Securities and Exchange Commission is effective. This prospectus is not
an offer to sell these securities and it is not soliciting an offer to buy these
securities in any jurisdiction where the offer or sale is not permitted.

AMEREN CORPORATION

Ameren is a public utility holding company registered under the Public
Utility Holding Company Act of 1935 and does not own any significant assets
other than the common stock of its subsidiaries. We were incorporated in
Missouri on August 7, 1995. On December 31, 1997, following the receipt of all
required approvals, CIPSCO Incorporated, or CIPSCO, and Union Electric Company,
or AmerenUE, combined with the result that the common shareholders of CIPSCO and
AmerenUE became the common shareholders of Ameren, and Ameren became the owner
of 100% of the common stock of AmerenUE and CIPSCO's subsidiaries, Central
Illinois Public Service Company, or AmerenCIPS, and CIPSCO Investment Company.
On January 31, 2003 and February 4, 2003, respectively, we completed our
acquisitions from The AES Corporation of all of the outstanding common stock of
CILCORP Inc. and the membership interests of AES Medina Valley Cogen (No. 4),
LLC. CILCORP is the parent company of Peoria, Illinois-based Central Illinois
Light Company, which we now operate as AmerenCILCO. AES Medina Valley Cogen
(No. 4), LLC has been renamed AmerenEnergy Medina Valley Cogen (No. 4), LLC, or
Medina Valley.

Our primary subsidiaries are as follows:

o Union Electric Company, which operates a rate-regulated electric
generation, transmission and distribution business, and a
rate-regulated natural gas transmission and distribution business in
Missouri and Illinois as AmerenUE. AmerenUE was incorporated in
Missouri in 1922 and is successor to a number of companies, the oldest
of which was organized in 1881. It is the largest electric utility in
Missouri and supplies electric and gas service in parts of central and
eastern Missouri and west central Illinois having an estimated
population of 2.6 million within an area of approximately 24,500
square miles, including the greater St. Louis area.

o Central Illinois Public Service Company, which operates a
rate-regulated electric and natural gas transmission and distribution
business in Illinois as AmerenCIPS. AmerenCIPS was incorporated in
Illinois in 1902. It supplies electric and gas utility service to
portions of central and southern Illinois having an estimated
population of 820,000 within an area of approximately 20,000 square
miles.

o Central Illinois Light Company, a subsidiary of CILCORP, which
operates a rate-regulated electric transmission and distribution
business, and a non rate-regulated electric generation business
principally through its subsidiary, AmerenEnergy Resources Generating
Company, or AERG, and a rate-regulated natural gas distribution
business in Illinois as AmerenCILCO. AmerenCILCO was incorporated in
Illinois in 1913. It supplies electric and gas utility service to
portions of central and east central Illinois in an area of
approximately 3,700 and 4,500 square miles, respectively. AERG was
incorporated in Illinois in November 2001 in conjunction with the
Illinois Electric Service Customer Choice and Rate Relief Law of 1997,
or the Illinois Customer Choice Law. AERG commenced operations on
October 3, 2003 when AmerenCILCO transferred its Duck Creek and E.D.
Edwards coal-fired plants and its Sterling Avenue combustion turbine
facilities representing in the aggregate approximately 1,100 megawatts
of electric generating capacity to AERG in exchange for all of the
outstanding stock of AERG and AERG's assumption of certain
liabilities.

o Ameren Energy Resources Company, which is a holding company for
certain of Ameren's non rate-regulated operations. Subsidiaries
include Ameren Energy Development Company, or Development Company, and
its subsidiary, Ameren Energy Generating Company, or Generating
Company, which operates a non rate-regulated electric generation
business in Missouri and Illinois; Ameren Energy Marketing Company,
which markets power for periods over one year; Ameren Energy Fuels and
Services Company, which procures fuel and manages the related risks
for our affiliated companies; and Medina Valley, which indirectly owns
a 40 megawatt, gas-fired electric generation plant.

o Generating Company, a subsidiary of Development Company, which
operates a non rate-regulated electric generation business. Generating
Company was incorporated in Illinois in March 2000 in conjunction with
the Illinois Customer Choice Law. Generating Company commenced
operations on May 1, 2000 when AmerenCIPS transferred its five
coal-fired plants located in Newton, Coffeen, Meredosia, Grand Tower
and Hutsonville, Illinois representing in the aggregate approximately
2,860 megawatts of electric generating capacity and related
liabilities to Generating Company at historical net book value.

o Ameren Energy, Inc., which serves as a power marketing and risk
management agent for our affiliated companies for transactions of
primarily less than one year.

o Electric Energy, Inc., which operates electric generation and
transmission facilities in Illinois. We have a 60% ownership interest
in Electric Energy, Inc., or EEI, and consolidate it for financial
reporting purposes.

o Ameren Services Company, which provides shared support services to us
and our subsidiaries.

On February 2, 2004, we entered into an agreement with Dynegy Inc. to
purchase the stock of Decatur, Illinois-based Illinois Power Company, or
Illinois Power, and Dynegy's 20% ownership interest in EEI. Illinois Power
operates a rate-regulated electric and natural gas transmission and distribution
business serving approximately 590,000 electric and 415,000 gas customers in
areas contiguous to our existing Illinois utility service territories. The total
transaction value is approximately $2.3 billion, including the assumption of
approximately $1.8 billion of Illinois Power debt and preferred stock. Upon
completion of the acquisition, expected by the end of 2004, Illinois Power will
become an Ameren subsidiary operating as AmerenIP. The transaction is subject to
the approval of the Illinois Commerce Commission, the Securities and Exchange
Commission, or SEC, the Federal Energy Regulatory Commission, the Federal
Communications Commission, the expiration of the waiting period under the
Hart-Scott-Rodino Act and other customary closing conditions.

In this prospectus, "Ameren," "we," "us" and "our" refer to Ameren
Corporation and, unless the context otherwise indicates, do not include our
subsidiaries.

WHERE YOU CAN FIND MORE INFORMATION

We have filed a registration statement on Form S-3 with the SEC under the
Securities Act of 1933. This prospectus is part of the registration statement,
but the registration statement also contains or incorporates by reference
additional information and exhibits. We are subject to the informational
requirements of the Securities Exchange Act of 1934 and, therefore, we file
annual, quarterly and current reports, proxy statements and other information
with the SEC. You may read and copy the registration statement and any document
that we file with the SEC at the SEC's public reference room at 450 Fifth
Street, N.W., Washington, D.C. 20549. You can call the SEC's toll-free telephone
number at 1-800-SEC-0330 for further information on the public reference room.
The SEC maintains a website at http://www.sec.gov that contains reports, proxy
and information statements and other information regarding companies, such as
us, that file documents with the SEC electronically. The documents can be found
by searching the EDGAR archives of the SEC electronically.

The SEC allows us to "incorporate by reference" the information that we
file with the SEC which means that we can disclose important information to you
by referring you to those documents. The information incorporated by reference
is considered to be part of this prospectus and you should read it with the same
care. Later information that we file with the SEC will automatically update and
supersede this information. We incorporate by reference the following documents
previously filed with the SEC:

o our Annual Report on Form 10-K for the year ended December 31, 2002,
as amended by Form 10-K/A;

o our Quarterly Reports on Form 10-Q for the quarters ended March 31,
2003, June 30, 2003 and September 30, 2003;

o our Current Reports on Form 8-K filed January 15, 2003, January 22,
2003, January 30, 2003, January 31, 2003, as amended by Form 8-K/A
filed March 7, 2003, March 5, 2003, May 23, 2003, June 2, 2003
(excluding that portion furnished under Item 9 of this report), July
18, 2003, October 3, 2003, October 10, 2003, December 5, 2003,
December 10, 2003, January 14, 2004, as amended by Form 8-K/A filed
January 14, 2004 and February 3, 2004; and

o the description of the rights to purchase shares of our Series A
junior participating preferred stock contained in our registration
statement on Form 8-A dated November 23, 1998.

We are also incorporating by reference all additional documents that we
file with the SEC under Sections 13(a), 13(c), 14 and 15(d) of the Securities
Exchange Act of 1934 between the date of the initial filing of the registration
statement of which this prospectus is a part and the effectiveness of the
registration statement, as well as between the date of this prospectus and the
time that all of the shares of common stock registered are sold.

Any statement contained in this prospectus or in a document incorporated or
deemed to be incorporated by reference in this prospectus will be deemed to be
modified or superseded for purposes of this prospectus to the extent that a
statement contained in this prospectus or in any separately filed document which
also is or is deemed to be incorporated by reference herein modifies or
supersedes that statement. Any statement so modified or superseded will not be
deemed, except as so modified or superseded, to constitute part of this
prospectus.

You may request a free copy of these filings by writing or telephoning us
at the following address:

Ameren Corporation
Attention: Secretary's Department
P.O. Box 66149
St. Louis, Missouri 63166-6149
Telephone: (314) 621-3222

You should rely only on the information incorporated by reference or
provided in this prospectus or any supplement. We have not authorized anyone
else to provide you with different information. If anyone provides you with
different or inconsistent information, you should not rely on it. We are not
making an offer to sell these shares of common stock under the Plan in any
jurisdiction where the offer or sale is not permitted. You should not assume
that the information in this prospectus or any supplement is accurate as of any
date other than the date on the front of those documents. Our business,
financial position, results of operations and prospects may have changed since
those dates.

DESCRIPTION OF THE PLAN

The provisions of the Plan in effect on and after the date hereof are
presented in the following questions and answers. If you are not a participant
in the Plan, you will continue to receive cash dividends, as declared, in the
usual manner.

PURPOSE

1. WHAT IS THE PURPOSE OF THE PLAN?

The purpose of the Plan is to provide participants (see Question 8) with a
convenient way to purchase our common stock and to reinvest all or a portion of
the cash dividends paid on the common stock and on the preferred stock of our
subsidiaries (together, Eligible Securities) in additional shares of our common
stock. When shares of our common stock purchased under the Plan are acquired
directly from us, we will receive additional equity funds which will be added to
our general funds and used for general corporate purposes as described in "Use
of Proceeds."

ADVANTAGES

2. WHAT ARE THE ADVANTAGES OF THE PLAN?

o Participants in the Plan may elect to have cash dividends on all or a
portion of their shares of common stock or preferred stock of our
subsidiaries automatically reinvested in common stock. Dividend
payments not reinvested will be paid to participants by check or
through electronic direct deposit.

o Participants in the Plan may make optional cash investments (including
by authorizing direct debit from their personal bank accounts) in a
minimum amount of $25 per transaction after the initial investment and
up to a maximum of $120,000 per calendar year for the purchase of
common stock.

o Full investment of funds is possible under the Plan because both full
and fractional shares will be credited to participants' Plan accounts.

o Participants may deposit their common stock certificates, at no cost,
in their Plan accounts for safekeeping.

o Participants may enroll and manage their Plan account through our
website at http://www.ameren.com.

o Personal recordkeeping is simplified by the issuance of statements
showing account activity. Statements of account are a participant's
continuing record of transactions and should be retained for tax
purposes.

o Participants may sell shares of common stock held or deposited in
their Plan accounts.

o By utilizing volume commission discounts from independent agents, the
Plan is able to provide investors with an economical means to purchase
and sell shares of our common stock.

DISADVANTAGES

3. WHAT ARE THE DISADVANTAGES OF THE PLAN?

A participant will have no control over the prices at which shares are
purchased or sold for his or her account, because:

o purchases for the participant's account will be made during periods
prescribed under the Plan. See Questions 11 and 16; and

o participants cannot designate a specific price or a specific date at
which to sell shares or select the broker through which sales will be
made. See Question 21.

Therefore, the participant will bear the risk of fluctuations in the market
price of our common stock.

OTHER FEATURES

4. WHAT ARE OTHER FEATURES OF THE PLAN?

o Non-shareholders of legal age may participate in the Plan by making a
minimum initial cash investment of $250 to purchase our common stock
under the terms of the Plan.

o Non-shareholders of legal age who are employees of Ameren or our
subsidiaries (an Employee) may authorize a minimum payroll deduction
investment of $25 in any pay period to purchase common stock under the
terms of the Plan.

o For each meeting of shareholders, participants will receive proxies
that will enable them to vote both shares registered in their names
and shares credited to their Plan accounts.

ADMINISTRATION

5. WHO ADMINISTERS THE PLAN?

Ameren Services Company, a wholly-owned subsidiary of Ameren, will
administer the Plan through its Banking and Investor Services Department
(Investor Services). Among other things, Ameren Services will receive and hold
participants' funds pending investment in additional shares of common stock,
effect transfers of common stock, keep a continuous record of participation and
prepare and send to each participant statements of the participant's Plan
account. The responsibilities of Ameren Services in connection with the
administration of the Plan are administrative in nature and, in large part, are
consistent with the responsibilities of Ameren Services in acting as our
registered transfer agent.

If we elect to meet the requirements of participants by purchasing shares
of common stock in the open market, an independent agent will act on behalf of
participants in buying such shares. An independent agent will also sell Plan
shares on behalf of participants.

We reserve the right to interpret and administer the Plan as deemed
necessary or desirable, including the right to limit or deny participation in
the Plan where circumstances warrant. The terms and conditions of the Plan and
its operation shall be governed by and construed in accordance with the laws of
the State of Missouri. Neither Ameren, Ameren Services, nor its independent
agents will be liable for any act done in good faith or for any omission to act
in good faith, provided that Ameren shall not be relieved from any liability
imposed under any federal, state or other applicable securities law which cannot
be waived. You should recognize that we cannot assure you of a profit or protect
you against a loss on shares purchased or sold under the Plan. A participant
participates in the Plan at his or her sole discretion, risk and responsibility.

6. WHO SHOULD I CONTACT WITH QUESTIONS CONCERNING THE PLAN AND ITS
ADMINISTRATION?

You may contact us with questions concerning the Plan

o by writing to:

Ameren Services Company
Banking and Investor Services Department
P.O. Box 66887
St. Louis, Missouri 63166-6887

o by calling Investor Services locally at (314) 554-3502 or
toll-free at (800) 255-2237

o by email at invest@ameren.com

o or by visiting our website at http://www.ameren.com.

Ameren Services acts as the transfer agent for all publicly-traded equity
securities issued by Ameren and its subsidiaries.

7. MAY THE PLAN BE SUSPENDED, MODIFIED OR DISCONTINUED?

We reserve the right to suspend, modify or discontinue the Plan at any
time, including, but not limited to the right to modify the fees and commissions
charged to participants. We will announce any suspension, major modification or
discontinuance of the Plan to all participants.

ELIGIBILITY

8. WHO IS ELIGIBLE TO PARTICIPATE IN THE PLAN?

Any person of legal age or entity, whether or not a holder of common stock
or preferred stock, is eligible to participate in the Plan provided that such
person or entity fulfills the prerequisites for participation described under
Question 9 and participation would not violate the securities or other laws of
the state, territory or country where the participant resides that are
applicable to Ameren, the Plan or the participant.

A Plan prospectus and enrollment or application information will be
furnished upon request made to Investor Services or it may be obtained from our
website at http://www.ameren.com.

PARTICIPATION

9. HOW DO I ENROLL IN THE PLAN OR CHANGE MY METHOD OF PARTICIPATION?

After receiving a copy of this prospectus, eligible applicants may become
participants in the Plan by completing and signing an enrollment form
(shareholders) or an application (non-shareholders). The minimum initial
optional cash investment is $25 for shareholders and $250 for non-shareholders.
The maximum aggregate optional cash investment that may be made by a participant
in any calendar year is $120,000.

The enrollment and application forms require a participant to choose a
reinvestment option for participation in the Plan. By checking the appropriate
box a participant may select:

o FULL DIVIDEND REINVESTMENT -- Automatic reinvestment of cash dividends
on all Eligible Securities registered in the name of the participant
and on all Plan shares credited to the participant's account.

o PARTIAL DIVIDEND REINVESTMENT -- Receipt of cash dividends on a
portion of the Eligible Securities registered in the name of the
participant and/or a portion of the Plan shares credited to the
participant's account, and automatic reinvestment of the cash
dividends on the remainder of the participant's shares.

o NO DIVIDEND REINVESTMENT -- Receipt of cash dividends on all Eligible
Securities registered in the name of the participant and on all Plan
shares credited to the participant's account.

Participants may change their reinvestment options by completing the
correspondence portion of their statement of account or an enrollment form and
sending it to Investor Services. Changes will become effective as soon as
practicable after they are received. Any change in reinvestment options must be
received by the dividend record date in order to be effective on the related
payment date.

10. HOW DOES AN EMPLOYEE PARTICIPATE?

An Employee may join the Plan at any time by enrolling in the same manner
as any other eligible person described under Question 9 or by completing a
Payroll Deduction Authorization form.

DIVIDEND REINVESTMENT

11. HOW AND WHEN WILL CASH DIVIDENDS BE REINVESTED?

If a participant has elected full or partial dividend reinvestment on the
Eligible Securities registered in the participant's name and/or the
participant's Plan shares, we will reinvest those dividends in additional shares
of our common stock. The source of common stock to be purchased under the Plan
may be, at our discretion, authorized but unissued or treasury shares of common
stock or shares of common stock purchased in the open market or in privately
negotiated transactions by an independent agent.

If we are meeting the requirements of the Plan with common stock purchased
in the open market or in privately negotiated transactions, an independent agent
will determine the exact timing of such purchases and the number of shares to be
purchased, depending on the amount of reinvested dividends, market conditions
and the requirements of federal securities laws, and the purchased shares will
be credited to a participant's Plan account as of the applicable Investment
Date, as defined below. If we elect to issue authorized but unissued or treasury
shares of our common stock, these shares will be issued by us and credited to a
participant's Plan account as of the applicable Investment Date. The
determination of the price for purchases of Plan shares is explained in
Question 18.

If a participant's enrollment form is received by Investor Services on or
before the record date with respect to any common stock or eligible preferred
stock cash dividend payment date, then the dividend payable on such payment date
will be used to purchase additional shares of common stock as of such payment
date (an Investment Date). If the enrollment form is received after the record
date for any such cash dividend payment date, the reinvestment of dividends will
start with the next dividend payment date.

Each cash dividend payment date on the Eligible Securities will be an
Investment Date under the Plan; accordingly, cash dividends payable on each
common stock dividend payment date and on preferred stock dividend payment date,
which are to be reinvested, will be invested in common stock as of such dividend
payment date. Common stock cash dividend payment dates are normally on or about
the last business day of March, June, September and December. Preferred stock
cash dividend payment dates vary depending upon the series of preferred stock
and the Ameren subsidiary issuing the preferred stock. You should contact
Investor Services for more information with respect to dividend payment dates.

OPTIONAL CASH INVESTMENTS

12. WHO IS ELIGIBLE TO MAKE OPTIONAL CASH INVESTMENTS?

All Plan participants, whether or not they have authorized the reinvestment
of dividends, are eligible to make optional cash investments.

13. HOW ARE OPTIONAL CASH INVESTMENTS MADE?

A Plan participant may make an initial cash investment when enrolling by
enclosing a check with the enrollment form or application. Checks should be made
payable to "Ameren Corporation," and returned in the envelope provided with the
enrollment form or application. Thereafter, optional cash investments may be
made by using the cash investment form attached to the statement of account, by
Automatic Cash Investment (see Question 14) or by Employee payroll deduction
(see Question 10). Please contact Investor Services for additional cash
investment forms.

14. WHAT IS THE AUTOMATIC CASH INVESTMENT OPTION OF THE PLAN AND HOW DOES IT
WORK?

The Automatic Cash Investment option offers participants in the Plan a
direct debit service. Optional cash investments are electronically withdrawn
from your personal checking or savings account at least once a month, usually
near the end of the month, and used to purchase common stock. The direct debit
from your personal bank account will be shown on the monthly statement from your
financial institution. In addition, you will receive a statement from Investor
Services detailing the cash received and shares purchased.

The Automatic Cash Investment option may be authorized for regular monthly
amounts from $25 to $10,000. Funds authorized for investment through the
Automatic Cash Investment option will be debited approximately three days prior
to the appropriate optional cash investment date. See Question 16.

For an Automatic Cash Investment application, please contact Investor
Services.

15. WHAT ARE THE LIMITATIONS ON MAKING OPTIONAL CASH INVESTMENTS?

Optional cash investments cannot be less than $25 per investment ($250 in
the case of the initial optional cash investment by a non-shareholder). The
maximum aggregate optional cash investment that may be made by a participant in
any calendar year cannot exceed $120,000.

16. WHEN WILL OPTIONAL CASH INVESTMENTS BE INVESTED?

The option to make cash investments is available to you at any time. The
dates on which optional cash investments are used to purchase common stock are
determined solely at our discretion, although purchases on behalf of Plan
participants will be made at least once a month. Purchases may be made over a
period of several days in the case of market purchases. All such purchases will
be aggregated and credited to participants' accounts on the optional cash
investment date occurring on or after receipt of the optional cash investment.
There will usually be an optional cash investment date on or about the 15th day
and the last day of each month. Participants will receive a notice at the
beginning of each year specifying the optional cash investment dates for such
year.

Cash received after an optional cash investment date will be invested as of
the next optional cash investment date. No interest will be paid by us on any
cash investments received by us pending investment.

PURCHASES

17. HOW MANY SHARES OF COMMON STOCK WILL BE PURCHASED?

The number of shares purchased for you under the Plan depends on the amount
of funds you have available for investment and the price of the shares. The
funds you have available for investment depends on what you have authorized in
regard to dividend reinvestment, plus any optional cash investments made. In
every case, your available funds will be fully invested in both whole and
fractional shares of common stock (computed to four decimal places). No one can
predict the number of shares that will be purchased for you during a particular
purchase period, and you cannot direct the purchase of a specific number of
shares.

18. WHAT IS THE PRICE OF SHARES PURCHASED FOR THE PLAN?

If shares for the Plan are being purchased in the open market or in
privately negotiated transactions, the price of such shares will be the weighted
average price at which the independent agent acquired the shares allocated to
participants' accounts on the applicable Investment Date plus applicable
brokerage commissions and other fees. If we are selling newly issued or treasury
shares of common stock, the price of such shares will be the average of the high
and low sales prices of our common stock on the applicable Investment Date
reported as on the consolidated tape for New York Stock Exchange listed
companies administered by the Consolidated Tape Association. The independent
agent may offset purchases of shares against sales of shares to be made for
participants under the Plan with respect to an Investment Date, resulting in a
net purchase or a net sale of shares.

19. WHO PURCHASES THE SHARES FOR THE PLAN?

We, at our discretion, may elect to satisfy the requirements of the Plan
with either unissued or treasury shares of common stock or shares of common
stock purchased in the open market or in privately negotiated transactions. If
we elect to purchase shares of common stock in the open market or in privately
negotiated transactions, the independent agent will make all such purchases
necessary to meet the requirements of the Plan. Other than establishing the
length of the investment period incorporated into the Plan, we do not exercise
any direct or indirect control over the timing or price of purchases made by the
independent agent. If open market or privately negotiated purchases are not
made, the shares issued under the Plan will be issued directly from the
authorized and unissued shares of our common stock or will be treasury shares.

20. ARE ANY FEES OR EXPENSES INCURRED BY PARTICIPANTS?

We will pay the costs of administering the Plan, but participants will be
required to pay brokerage commissions and other fees for shares purchased in the
open market or in privately negotiated transactions and shares sold through the
Plan as well as any transfer tax, if applicable. Brokerage commissions will be
at a negotiated rate established under the terms of our agreements with
independent agents. See Question 7.

SALES AND TERMINATION FROM THE PLAN

21. MAY PARTICIPANTS SELL OR WITHDRAW ALL OR A PORTION OF THEIR SHARES FROM
THE PLAN?

Yes. Any participant may withdraw from the Plan, request that a certificate
be issued for Plan shares or request that Plan shares be sold and the cash
proceeds forwarded to the participant. Participation in the Plan is entirely
voluntary. Participants may sell or withdraw all or a portion of their shares by
filling out the correspondence portion of their account statement or by
contacting Investor Services.

A stock certificate for any whole number of shares will be issued from your
Plan account as soon as practicable after requested. If you would like stock
certificates issued in a registration other than the name on your account,
contact Investor Services.

Investor Services will aggregate Plan sale requests and place a market
order with the independent agent to sell such shares at least four times a
month. The participant will receive the proceeds of the sale less any brokerage
commission and any other fees as soon as practicable after the settlement date
for the applicable sale.

If a participant's request for a sale or withdrawal is received by Investor
Services on or soon after a dividend payment date, such request will be
processed as soon as practicable after reinvested dividends have been allocated.

If a participant's Plan account contains less than one full share, Investor
Services reserves the right to sell any fractional share remaining in the
account, forward the proceeds of the sale to the participant and terminate the
account.

REPORTS TO PARTICIPANTS

22. HOW WILL PARTICIPANTS BE ADVISED OF THEIR PURCHASE OF SHARES OF COMMON
STOCK AND OTHER ACTIVITY IN THEIR PLAN ACCOUNTS?

Participants will receive a quarterly statement as soon as practicable
following the end of each calendar quarter. The last quarterly statement of each
calendar year will reflect year-to-date Plan activity. In addition, a statement
will be provided in any month an account has Plan activity. These statements are
participants' continuing record of their Plan transactions and should be
retained for tax purposes. Participants should be aware that it is important to
retain all statements received as there will be a fee incurred to provide
historical statement information.

Participants will receive copies of the same communications sent to other
registered shareholders of common stock, including our annual report, notice of
annual meeting and proxy statement, and certain tax information.

CERTIFICATES

23. WILL STOCK CERTIFICATES AUTOMATICALLY BE ISSUED FOR SHARES OF COMMON STOCK
ACQUIRED UNDER THE PLAN?

No. Unless you request otherwise as described below, the number of shares
credited to your Plan account will be held by Ameren Services, as agent, and
will be shown on your statement of account. This service protects against loss,
theft or destruction of stock certificates.

A certificate for any number of whole shares up to the full number of
shares credited to your Plan account will be issued to you if you so request in
writing. See Question 21. Such request should be mailed to Investor Services.

Shares credited to your Plan account may not be used as collateral. If you
wish to use your Plan shares as collateral, you must request that a certificate
be issued in your name. A certificate for fractional shares will not be issued
under any circumstances.

TRANSFER OF SHARES HELD IN THE PLAN

24. CAN PLAN SHARES BE TRANSFERRED?

Upon written request, Plan shares can be transferred into names other than
the account name, subject to compliance with any applicable laws and the payment
by the participant of any applicable taxes, provided that the request is
accompanied by a duly executed stock power that bears the signature(s) of the
participant(s) and the signature(s) is/are Medallion Guaranteed by a financial
institution, such as a commercial bank or a brokerage firm, that is a member of
either the STAMP, SEMP or MSP Medallion Guarantee programs. Unless instructed
otherwise, Ameren Services will hold the transferred shares in an account in the
transferee's name in the Plan and apply the same dividend reinvestment options
as existed with respect to the transferred account.

SAFEKEEPING SERVICE FOR COMMON STOCK CERTIFICATES

25. WHAT IS THE PLAN'S SAFEKEEPING SERVICE AND HOW DOES IT WORK?

The Plan's safekeeping service allows you to deposit your common stock
certificate(s) into your Plan account. The benefits of this service include the
convenience of keeping all of your shares in one place, and the protection
against the cost of replacing your certificates should they be lost, stolen or
destroyed. If you would like to take advantage of this service, please contact
Investor Services.

ONLINE SERVICES

26. WHAT TRANSACTIONS CAN A PARTICIPANT CONDUCT THROUGH OUR WEBSITE?

Through our website, a participant may:

o enroll in the Plan;

o authorize the reinvestment of his or her common stock or
preferred stock cash dividends; and

o authorize optional cash investments;

and a participant may:

o review and manage his or her Plan account at his or her
convenience;

o arrange for sales of some or all of his or her shares of common
stock; and

o request the issuance of a stock certificate for some or all of
his or her shares of common stock.

Participation in the Plan through our online services is voluntary. A
participant can access such services at our website at http://www.ameren.com.

INCOME TAXES

27. WHAT ARE THE FEDERAL INCOME TAX CONSEQUENCES OF PARTICIPATION IN THE PLAN?

In general, participants in the Plan have the same federal income tax
obligations with respect to their dividends as do shareholders who are not Plan
participants. This means that dividends reinvested under the Plan are taxable as
having been received even though the participants did not actually receive them
in cash but, instead, used them to purchase additional shares under the Plan.

Federal legislation enacted in 2003 has lowered the tax rate that is
applicable to most dividends. For participants who have held their Ameren common
stock for more than a 60-day period surrounding the ex-dividend date, the
dividend will be taxed at the 5% or 15% rates which apply to long-term capital
gains.

The sale of shares by a participant under the Plan may give rise to a
capital gain or loss, provided such shares are held as a capital asset by the
participant. Any such gain or loss will be measured by the difference between
the proceeds received by the participant (net of commissions and fees) and the
participant's tax basis in the shares sold.

For participants who are subject to U.S. withholding tax, backup
withholding or foreign taxes, we will withhold the required taxes from the gross
dividends or proceeds from the sale of shares. The dividends or proceeds
received by the participant, or dividends reinvested on behalf of the
participant, will be net of the required taxes.

The foregoing is only a general statement of federal income tax
consequences. Each participant should consult his or her own tax advisor as to
the specific application of the tax laws and regulations governing the Plan as
they relate to such participant. The statements of account sent to participants
should be retained for tax purposes.

DESCRIPTION OF COMMON STOCK

GENERAL

The following descriptions of our common stock and the relevant provisions
of our restated articles of incorporation and by-laws are summaries and are
qualified by reference to our restated articles of incorporation and by-laws
which have been previously filed with the SEC and are exhibits to this
registration statement, of which this prospectus is a part, as well as the
applicable Missouri General and Business Corporation Law.

Under our restated articles of incorporation, we are authorized to issue
400 million shares of common stock, $.01 par value per share, and 100 million
shares of preferred stock, $.01 par value per share. At February 11, 2004,
181,993,522 shares of common stock and no shares of preferred stock were
outstanding. In March 2002, we issued equity security units pursuant to which we
may issue between 7,402,320 and 8,734,020 additional shares of common stock on
or before May 15, 2005 in settlement of the purchase contracts comprising a
portion of the units.

DIVIDEND RIGHTS AND LIMITATIONS

The holders of our common stock are entitled to receive such dividends as
our board of directors may from time to time declare, subject to any rights of
the holders of our preferred stock, if any is issued. Our ability to pay
dividends depends primarily upon the ability of our subsidiaries to pay
dividends or otherwise transfer funds to us. Various financing arrangements,
charter provisions and regulatory requirements may impose certain restrictions
on the ability of our subsidiaries to transfer funds to us in the form of cash
dividends, loans or advances.

VOTING RIGHTS

Except as otherwise provided by law and subject to the voting rights of
holders of our preferred stock, the holders of our common stock have the
exclusive right to vote for the election of directors and for all other
purposes. Each holder of our common stock is entitled to one vote per share on
all matters submitted to a vote at a meeting of shareholders, including the
election of directors, which means that the holders of more than 50% of the

shares voting for the election of directors can elect 100% of the directors and
the holders of the remaining shares voting for the election of directors will
not be able to elect any directors. The common stock shall vote together as a
single class. The holders of our common stock are not entitled to cumulate votes
for the election of directors. At annual and special meetings of shareholders, a
majority of the outstanding shares of common stock constitutes a quorum.

LIQUIDATION RIGHTS

In the event of any liquidation, dissolution or winding up of our affairs,
voluntarily or involuntarily, the holders of our common stock will be entitled
to receive the remainder, if any, of our assets after the payment of all our
debts and liabilities and after the payment in full of any preferential amounts
to which holders of any preferred stock may be entitled.

MISCELLANEOUS

The outstanding shares of common stock are, and the shares of common stock
sold hereunder will be, upon payment for them, fully paid and nonassessable. The
holders of our common stock are not entitled to any preemptive or preferential
rights to subscribe for or purchase any part of any new or additional issue of
stock or securities convertible into stock. Our common stock does not contain
any redemption provisions or conversion rights.

TRANSFER AGENT AND REGISTRAR

Ameren Services acts as transfer agent and registrar for the common stock.

SHAREHOLDER RIGHTS PLAN

On October 9, 1998, our board of directors adopted a shareholder rights
plan and declared a dividend of one preferred share purchase right for each
outstanding share of our common stock. The plan is designed to assure
shareholders of fair and equal treatment in the event of a proposed takeover.
Each right entitles the registered holder to purchase from us one one-hundredth
of a share of Series A junior participating preferred stock, par value $.01 per
share, at an exercise price of $180 per one one-hundredth of a share of such
preferred stock, subject to adjustment. The rights will become exercisable only
if a person or group acquires 15% or more of our common stock or announces a
tender offer, the consummation of which would result in ownership by a person or
group of 15% or more of our common stock. If a person or group acquires 15% or
more of our outstanding common stock, each right will entitle its holder (other
than such person or members of such group) to purchase, at the right's
then-current exercise price, a number of shares of our common stock having a
market value of twice such price. In addition, if we are acquired in a merger or
other business combination transaction after a person or group has acquired 15%
or more of our outstanding common stock, each right will entitle its holder to
purchase, at the right's then-current exercise price, a number of shares of the
acquiring company's common stock having a market value of twice such price. The
acquiring person or group will not be entitled to exercise these rights.

The SEC approved the plan under the Public Utility Holding Company Act of
1935 in December 1998. The rights were issued as a dividend payable January 8,
1999, to shareholders of record on that date. The rights will expire on
October 9, 2008. One right will accompany each new share of our common stock
issued prior to such expiration date. The rights do not have voting or dividend
rights, and until they become exercisable, have no dilutive effect on our
per-share earnings.

We have 4 million shares of preferred stock initially reserved for issuance
upon exercise of the rights. There is no junior participating preferred stock
issued or outstanding as of the date of this prospectus.

The description and terms of the rights are set forth in an agreement
between us and EquiServe Trust Company, N.A. (successor to First Chicago Trust
Company of New York), as rights agent. The proceeding summary of the rights and
the shareholder rights plan is qualified in its entirety by reference to the
rights agreement and the description thereof each contained in our registration
statement on Form 8-A dated November 23, 1998, which is incorporated by
reference into this prospectus.

CERTAIN ANTI-TAKEOVER MATTERS

Our restated articles of incorporation and by-laws include a number of
provisions that may have the effect of discouraging persons from acquiring large
blocks of our stock or delaying or preventing a change in our control. The
material provisions that may have such an effect include:

o authorization for our board of directors (subject to any required
regulatory approval) to issue our preferred stock in series and to fix
rights and preferences of the series (including, among other things,
whether, and to what extent, the shares of any series will have voting
rights and the extent of the preferences of the shares of any series
with respect to dividends and other matters);

o advance notice procedures with respect to nominations of directors or
proposals other than those adopted or recommended by our board of
directors;

o the prohibition of shareholder action by less than unanimous written
consent without a meeting; and

o provisions specifying that only the chief executive officer or the
board of directors (by a majority vote of the entire board of
directors) may call special meetings of shareholders, and that the
chairman of the meeting may adjourn a meeting of shareholders from
time to time, whether or not a quorum is present.

In addition, the Missouri General and Business Corporation Law, or the
MGBCL, contains certain provisions, including business combination provisions
that would be applicable to certain mergers, share exchanges or sales of
substantially all assets involving us or a subsidiary and a significant
shareholder and which could have the effect of substantially increasing the cost
to the acquiror and thus discouraging any such transaction. The MGBCL permits
shareholders to adopt an amendment to the articles of incorporation opting out
of the business combination provisions, and our restated articles of
incorporation opt out of such provisions.

Under the Illinois Public Utilities Act, approval of the Illinois Commerce
Commission is required for any transaction which, regardless of the means by
which it is accomplished, results in a change in the ownership of a majority of
the voting capital stock of an Illinois public utility or the ownership or
control of any entity which owns or controls a majority of the voting capital
stock of a public utility. Because we control a majority of the voting stock of
AmerenCIPS, AmerenUE and AmerenCILCO, each public utilities subject to Illinois
utility regulation, any change in our ownership or control, within the meaning
of the Illinois Public Utilities Act, would require Illinois Commerce Commission
approval. Certain acquisitions by any person of our outstanding voting shares
would also require approval of the SEC under the Public Utility Holding Company
Act of 1935.

USE OF PROCEEDS

The number of shares of common stock, if any, that we will sell under the
Plan and the prices at which such shares will be sold cannot presently be
determined. The number and prices of shares sold will be affected by the level
of participation in the Plan, the prevailing prices of our common stock and
whether the shares are newly issued or treasury shares or shares purchased in
the open market or privately negotiated transactions. If newly issued or
treasury shares of common stock are sold by us under the Plan, we will use the
net proceeds we receive from the sale:

o to finance our subsidiaries' ongoing construction and maintenance
programs;

o to redeem, repurchase, repay or retire outstanding indebtedness,
including indebtedness of our subsidiaries;

o to finance strategic investments in, or future acquisitions of, other
entities or their assets; and

o for other general corporate purposes.

If shares are purchased by an independent agent in the open market or in
private transactions for sale under the Plan, we will not receive any proceeds
from such sales.

LEGAL MATTERS

Steven R. Sullivan, Esq., our Senior Vice President Governmental/Regulatory
Policy, General Counsel and Secretary, has issued a legal opinion as to certain
legal matters in connection with the common stock offered by this prospectus. As
of December 31, 2003, Mr. Sullivan owned 502 shares of Ameren's common stock. In
addition, as of that date, Mr. Sullivan had been granted options to purchase
30,100 shares of Ameren's common stock, of which options to purchase 20,375
shares were fully vested, and he owned 7,921 restricted shares of Ameren's
common stock, none of which were fully unrestricted.

EXPERTS

The consolidated financial statements incorporated in this prospectus by
reference to our Annual Report on Form 10-K, as amended by Form 10-K/A, for the
year ended December 31, 2002 have been so incorporated in reliance upon the
report of PricewaterhouseCoopers LLP, independent accountants, given on the
authority of said firm as experts in auditing and accounting.

======================================== ===============================

No dealer, salesperson or other
person is authorized to give any
information to or represent anything
not contained in this prospectus. You AMEREN CORPORATION
must not rely on any unauthorized
information or representations. This
prospectus is an offer to sell only
the shares offered hereby, but only DRPLUS
under circumstances and in DIVIDEND REINVESTMENT
jurisdictions where it is lawful to do AND STOCK PURCHASE PLAN
so. The information contained in this
prospectus is current only as of its
date.

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

TABLE OF CONTENTS Common Stock

Page
----

------------
Ameren Corporation...................2
Where You Can Find More Information..3
Description of the Plan..............4 PROSPECTUS
Description of Common Stock.........12
Use of Proceeds.....................14
Legal Matters.......................15
Experts.............................15 ------------

======================================== ===============================

PART II. INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. Other Expenses of Issuance and Distribution

Securities and Exchange Commission registration fee........... $ 5,221*
Stock exchange listing fees................................... 21,000
Printing expenses............................................. 15,000
Fees of accountants........................................... 4,000
Fees of attorneys............................................. 25,000
Blue sky fees................................................. 5,000
Miscellaneous expenses........................................ 3,775
--------
Total.................................................... $105,000
========
--------------
* Actual expenses; all other expenses are estimates

ITEM 15. Indemnification of Directors and Officers

Article IV of the By-laws of Ameren Corporation (the "Company"), consistent
with the applicable provisions of the Missouri General and Business Corporation
Law (the "MGBCL"), provides for indemnification of directors and officers. These
provisions provide that any person shall be indemnified for expenses and
liabilities imposed upon such person in connection with any threatened, pending
or completed action, suit, or proceeding, whether civil, criminal,
administrative or investigative, other than an action by or in the right of the
Company, by reason of the fact that such person is or was a director, officer,
employee or agent of the Company, or is or was serving at the request of the
Company as a director, officer, employee or agent of another corporation,
partnership, joint venture, trust or other enterprise, against expenses,
including attorneys' fees, judgments, fines and amounts paid in settlement
actually and reasonably incurred by such person in connection with such action,
suit or proceeding if such person acted in good faith and in a manner such
person reasonably believed to be in or not opposed to the best interests of the
Company, and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his conduct was unlawful.

In a proceeding brought by or in the right of the Company, indemnification
shall be made with respect to any claim as to which an officer or director has
been adjudged to have been liable to the Company if such person acted in good
faith and in a manner he reasonably believed to be in or not opposed to the best
interests of the Company. However, no indemnification shall be made in respect
of any claim, issue or matter as to which such person shall have been adjudged
to be liable for negligence or misconduct in the performance of his duty to the
Company unless and only to the extent that the court in which the action or suit
was brought determines upon application that, despite the adjudication of
liability and in view of all the circumstances of the case, the person is fairly
and reasonably entitled to indemnity for such expenses which the court shall
deem proper.

The By-laws, consistent with the applicable provisions of the MGBCL,
provide that indemnification shall be made by the Company only if a
determination has been made by a majority vote of a quorum of the disinterested
directors or by the shareholders or by independent legal counsel, that the
director or officer met the required standard of conduct. The Company has
purchased insurance on behalf of its officers and directors which insures them
against certain liabilities and expenses, including those under the Securities
Act of 1933.

The By-laws, consistent with the applicable provisions of the MGBCL,
further provide that, in addition to the indemnities described in the preceding
paragraphs, the Company will further indemnify its officers and directors to the
maximum extent permitted by law, provided that no indemnity may be given for
conduct that is adjudged to be knowingly fraudulent, deliberately dishonest, or
willful misconduct.

II-1

ITEM 16. Exhibits

EXHIBIT
NO. DESCRIPTION
------- ----------------------------------------------------------------------

*2.1 Stock Purchase Agreement, dated as of February 2, 2004, among the
Company, Dynegy Inc., Illinova Corporation and Illinova Generating
Company (February 3, 2004 Form 8-K, Exhibit 2.1).

*4.1 Restated Articles of Incorporation of the Company (File No. 33-64165,
Annex F).

*4.2 Certificate of Amendment to the 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)).

4.3 By-laws of the Company as amended to February 13, 2004.

*4.4 Agreement, dated as of October 9, 1998, between the Company 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).

5 Opinion of Steven R. Sullivan, Esq., Senior Vice President
Governmental/Regulatory Policy, General Counsel and Secretary of the
Company, regarding the validity of the securities.

23.1 Consent of Steven R. Sullivan (included in Exhibit 5).

23.2 Consent of independent accountants.

24 Powers of Attorney.

NOTE: REPORTS OF THE COMPANY ON FORMS 8-K, 10-Q AND 10-K ARE ON FILE WITH
THE SEC UNDER FILE NUMBER 1-14756.

-------------------
* Incorporated by reference herein as indicated.

ITEM 17. Undertakings

The undersigned registrant hereby undertakes:

(1) To file, during any period in which offers or sales are being made, a
post-effective amendment to this registration statement:

(i) To include any prospectus required by section 10(a)(3) of the
Securities Act of 1933;

(ii) To reflect in the prospectus any facts or events arising after
the effective date of the registration statement (or the most recent
post-effective amendment thereof) which, individually or in the aggregate,
represent a fundamental change in the information set forth in the
registration statement. Notwithstanding the foregoing, any increase or
decrease in volume of securities offered (if the total dollar value of
securities offered would not exceed that which was registered) and any
deviation from the low or high end of the estimated maximum offering range
may be reflected in the form of prospectus filed with the Securities and
Exchange Commission pursuant to Rule 424(b) if, in the aggregate, the
changes in volume and price represent no more than a 20 percent change in
the maximum aggregate offering price set forth in the "Calculation of
Registration Fee" table in the effective registration statement; and

(iii) To include any material information with respect to the plan of
distribution not previously disclosed in the registration statement or any
material change to such information in the registration statement;

provided, however, that (i) and (ii) do not apply if the registration statement
is on Form S-3 or Form S-8, and the information required to be included in a
post-effective amendment by those paragraphs is contained in periodic reports
filed with or furnished to the Securities and Exchange Commission by the Company

II-2

pursuant to section 13(a) or section 15(d) of the Securities Exchange Act of
1934 that are incorporated by reference in the registration statement.

(2) That, for the purpose of determining any liability under the Securities
Act of 1933, each such post-effective amendment shall be deemed to be a new
registration statement relating to the securities offered therein and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

(3) To remove from registration by means of a post-effective amendment any
of the securities being registered which remain unsold at the termination of the
offering.

(4) That, for purposes of determining any liability under the Securities
Act of 1933, each filing of the Company's annual report pursuant to
section 13(a) or section 15(d) of the Securities Exchange Act of 1934 (and,
where applicable, each filing of an employee benefit plan's annual report
pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is
incorporated by reference in this registration statement shall be deemed to be a
new registration statement relating to the securities offered herein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

Insofar as indemnification for liabilities arising under the Securities Act
of 1933 may be permitted to directors, officers and controlling persons of the
registrant pursuant to the provisions described under Item 15 above, or
otherwise, the registrant has been advised that in the opinion of the Securities
and Exchange Commission such indemnification is against public policy as
expressed in the Securities Act of 1933 and is, therefore, unenforceable. In the
event that a claim for indemnification against such liabilities (other than the
payment by the registrant of expenses incurred or paid by a director, officer or
controlling person of the registrant in the successful defense of any action,
suit or proceeding) is asserted by such director, officer or controlling person
in connection with the securities being registered, the registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the
Securities Act of 1933 and will be governed by the final adjudication of such
issue.

II-3

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Company
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-3 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of St. Louis, State of Missouri, on the 13th day of
February, 2004.

AMEREN CORPORATION (Registrant)

By: /s/ Gary L. Rainwater
---------------------------------
Gary L. Rainwater
Chairman, President and Chief
Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed by the following persons in the
capacities and on the date indicated.

NAME TITLE DATE
---- ----- ----

Chairman, President, Chief
/s/ Gary L. Rainwater Executive Officer and
------------------------------- Director February 13, 2004
Gary L. Rainwater (Principal Executive Officer)

/s/ Warner L. Baxter Executive Vice President and
------------------------------- Chief Financial Officer February 13, 2004
Warner L. Baxter (Principal Financial Officer)

/s/ Martin J. Lyons Vice President and Controller
------------------------------- (Principal Accounting Officer) February 13, 2004
Martin J. Lyons

*
------------------------------- Director February 13, 2004
William E. Cornelius

*
------------------------------- Director February 13, 2004
Susan S. Elliott

*
------------------------------- Director February 13, 2004
Clifford L. Greenwalt

*
------------------------------- Director February 13, 2004
Thomas A. Hays

NAME TITLE DATE
---- ----- ----

*
------------------------------ February 13, 2004
Richard A. Liddy Director

*
------------------------------ Director February 13, 2004
Gordon R. Lohman

*
------------------------------ Director February 13, 2004
Richard A. Lumpkin

*
------------------------------ Director February 13, 2004
John Peters MacCarthy

*
------------------------------ Director February 13, 2004
Paul L. Miller, Jr.

*
------------------------------ Director February 13, 2004
Charles W. Mueller

*
------------------------------ Director February 13, 2004
Douglas R. Oberhelman

*
------------------------------ Director February 13, 2004
Harvey Saligman

*By: /s/ Steven R. Sullivan
-------------------------
Steven R. Sullivan
Attorney-in-Fact

EXHIBIT INDEX

EXHIBIT
NO. DESCRIPTION
-------- ----------------------------------------------------------------------
*2.1 Stock Purchase Agreement, dated as of February 2, 2004, among the
Company, Dynegy Inc., Illinova Corporation and Illinova Generating
Company (February 3, 2004 Form 8-K, Exhibit 2.1).