As filed with the Securities and Exchange Commission on August 10, 2005
                                                     Registration No. 333-______
================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

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

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

           MISSOURI                                              43-1723446
(State or other jurisdiction of                               (I.R.S. Employer
 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)

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

        Ameren Corporation Employee Long-Term Savings Plan - IBEW No. 702
                            (Full title of the plan)

                                WARNER L. BAXTER
              Executive Vice President and Chief Financial Officer

                               STEVEN R. SULLIVAN
              Senior Vice President, General Counsel and Secretary
                              1901 Chouteau Avenue
                            St. Louis, Missouri 63103
                                 (314) 621-3222
          (Names and address, including zip code, and telephone number,
                   including area code, of agents for service)




                                         CALCULATION OF REGISTRATION FEE
========================================================================================================================
                                                           PROPOSED MAXIMUM    PROPOSED MAXIMUM
TITLE OF EACH CLASS OF SECURITIES       AMOUNT TO BE        OFFERING PRICE         AGGREGATE             AMOUNT OF
        TO BE REGISTERED            REGISTERED (1)(2)(3)    PER SHARE (3)      OFFERING PRICE (4)   REGISTRATION FEE (5)
------------------------------------------------------------------------------------------------------------------------
                                                                                                   
Common Stock, $.01 par value           200,000 shares           $54.45            $10,890,000               $1,282
(including associated preferred
share purchase rights)
========================================================================================================================

(1)  In addition, pursuant to Rule 416(a) under 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
     employee benefit plan described herein.
(2)  In addition, pursuant to Rule 416(c) under the Securities Act of 1933, this
     registration statement also covers an indeterminate amount of interests to
     be offered or sold pursuant to the employee benefit plan described herein.
(3)  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.
(4)  Estimated solely for purposes of calculating the registration fee pursuant
     to Rule 457(h) 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 August 8, 2005.
(5)  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.



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





           PART II. INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

     The following documents, previously filed with the Securities and Exchange
Commission ("SEC") by Ameren Corporation (the "Company") and the Ameren
Corporation Employee Long-Term Savings Plan - IBEW No. 702 (the "Plan") pursuant
to the Securities Exchange Act of 1934 are incorporated by reference in this
registration statement:

     (1)  the Company's Annual Report on Form 10-K for the year ended December
          31, 2004;

     (2)  the Company's Quarterly Reports on Form 10-Q for the quarters ended
          March 31, 2005 and June 30, 2005;

     (3)  the Company's Current Reports on Form 8-K filed January 27, 2005,
          February 8, 2005 (excluding any portion of such report that was
          furnished), February 14, 2005 (Form 8-K/A), February 14, 2005, April
          7, 2005, May 2, 2005, July 15, 2005 and July 21, 2005;

     (4)  the description of the rights to purchase shares of the Company's
          Series A junior participating preferred stock contained in the
          Company's registration statement on Form 8-A dated November 23, 1998;
          and

     (5)  the Annual Report on Form 11-K for the year ended December 31, 2004 of
          the Plan.

     All documents subsequently filed by the Company pursuant to Sections 13(a),
13(c), 14 or 15(d) of the Securities Exchange Act of 1934 prior to the filing of
a post-effective amendment which indicates that all securities offered have been
sold or which deregisters all the securities then remaining unsold, shall be
deemed to be incorporated herein by reference and to be a part hereof from the
respective dates of filing thereof. Any statement contained in an incorporated
document shall be deemed to be modified or superseded to the extent that a
statement contained herein or in any subsequently filed incorporated document
modifies or supersedes such statement.

ITEM 4.  DESCRIPTION OF SECURITIES.

                           DESCRIPTION OF COMMON STOCK

GENERAL

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

     Under the Company's restated articles of incorporation, the Company is
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
June 30, 2005, 203,710,912 shares of common stock and no shares of preferred
stock were outstanding.

DIVIDEND RIGHTS AND LIMITATIONS

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


                                      II-2



VOTING RIGHTS

     Except as otherwise provided by law and subject to the voting rights of
holders of the Company's preferred stock, the holders of the Company's common
stock have the exclusive right to vote for the election of directors and for all
other purposes. Each holder of the Company's 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 the Company's 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 the Company's
affairs, voluntarily or involuntarily, the holders of the Company's common stock
will be entitled to receive the remainder, if any, of the Company's assets after
the payment of all the Company's 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 the Company's 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. The Company's
common stock does not contain any redemption provisions or conversion rights.

TRANSFER AGENT AND REGISTRAR

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

SHAREHOLDER RIGHTS PLAN

     On October 9, 1998, the Company's board of directors adopted a shareholder
rights plan and declared a dividend of one preferred share purchase right for
each outstanding share of the Company's 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 the Company
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 the Company's
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 the Company's common stock.
If a person or group acquires 15% or more of the Company's 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 the Company's common stock having a market value of twice such price.
In addition, if the Company is acquired in a merger or other business
combination transaction after a person or group has acquired 15% or more of the
Company's 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 the Company's 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 the
Company's per-share earnings.


                                      II-3



     The Company has 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 the filing of this registration
statement.

     The description and terms of the rights are set forth in an agreement
between the Company and EquiServe Trust Company, N.A. (successor to First
Chicago Trust Company of New York), as rights agent. The preceding 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
the Company's registration statement on Form 8-A dated November 23, 1998, which
is incorporated by reference.

CERTAIN ANTI-TAKEOVER MATTERS

     The Company's 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 the Company's stock or delaying or preventing a change
in the Company's control. The material provisions that may have such an effect
include:

     o    authorization for the Company's board of directors (subject to any
          required regulatory approval) to issue the Company's 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 the Company's
          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 the Company 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 the Company's 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 the Company controls a majority of the voting
stock of Central Illinois Public Service Company, or AmerenCIPS, Central
Illinois Light Company, or AmerenCILCO, and Illinois Power Company, or AmerenIP,
each public utilities subject to Illinois utility regulation, any change in the
Company's ownership or control, within the meaning of the Illinois Public
Utilities Act, would require Illinois Commerce Commission approval. Certain
acquisitions by any person of the Company's outstanding voting shares would also
require approval of the SEC under the Public Utility Holding Company Act of
1935.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Steven R. Sullivan, Esq., the Company's Senior Vice President, General
Counsel and Secretary, will pass upon the validity of the offered securities. As
of June 30, 2005, Mr. Sullivan owned 612 shares of the Company's common stock.
In addition, as of that date, Mr. Sullivan owned 16,837 restricted shares of the
Company's common stock, none of which were fully unrestricted.


                                      II-4



     The consolidated financial statements and management's assessment of the
effectiveness of internal control over financial reporting (which is included in
Management's Report on Internal Control Over Financial Reporting) incorporated
in this registration statement by reference to the Annual Report on Form 10-K
for the year ended December 31, 2004, and the financial statements incorporated
in this registration statement by reference to the Plan's Annual Report on Form
11-K for the year ended December 31, 2004, have been so incorporated in reliance
on the report of PricewaterhouseCoopers LLP, an independent registered public
accounting firm, given on the authority of said firm as experts in auditing and
accounting.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Article IV of the Company's By-laws, consistent with the applicable
provisions of 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.

ITEM 8.  EXHIBITS.

Exhibit
Number    Description of Exhibit
-------   ----------------------

**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, 1997 (1998 Form 10-K, Exhibit 3(i), File No. 1-14756).

**4.3     By-laws of the Company as amended February 13, 2004 (Exhibit 4.3,
          File No. 333-112823).


                                      II-5



**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, File No. 1-14756).

*5        Opinion of Steven R. Sullivan, Esq., Senior Vice President, General
          Counsel and Secretary of the Company, regarding the legality of the
          securities.

*23.1     Consent of Steven R. Sullivan, Esq. (included in opinion, attached
          hereto as Exhibit 5).

*23.2     Consent of independent registered public accounting firm.

*24       Power of Attorney.

-----------
*    Filed herewith.

**   Incorporated herein by reference as indicated.

     UNDERTAKING. The Company will submit or has submitted the Plan and any
amendment thereto to the Internal Revenue Service ("IRS") in a timely manner and
has made or will make all changes required by the IRS in order to qualify the
Plan under Section 401 of the Internal Revenue Code.

ITEM 9.  UNDERTAKINGS.

a.   The undersigned 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 SEC pursuant to Rule 424(b) if, in the
                aggregate, the changes in volume and price represent no more
                than 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 paragraphs (a)(1)(i) and (a)(1)(ii) do not
          apply if 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 SEC by the Company pursuant to Section 13 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.


                                      II-6



     (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 Act of 1933)
          that is incorporated by reference in the 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.

b.   Insofar as indemnification for liabilities arising under the Securities Act
     of 1933 may be permitted to directors, officers and controlling persons of
     the Company pursuant to the provisions described under Item 6 above, or
     otherwise, the Company has been advised that in the opinion of the SEC 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
     Company of expenses incurred or paid by a director, officer or controlling
     person of the Company 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 Company 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-7



                                   SIGNATURES

     THE REGISTRANT. Pursuant to the requirements of the Securities Act of 1933,
the registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8 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, and State of Missouri, on the 10th
day of August, 2005.

                                         AMEREN CORPORATION (REGISTRANT)


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

     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 dates indicated.

          SIGNATURE                        TITLE                      DATE
          ---------                        -----                      ----

    /s/ Gary L. Rainwater         Chairman, Chief Executive      August 10, 2005
-----------------------------      Officer and President
      Gary L. Rainwater         (Principal Executive Officer)


    /s/ Warner L. Baxter        Executive Vice President and     August 10, 2005
-----------------------------      Chief Financial Officer
      Warner L. Baxter          (Principal Financial Officer)


    /s/ Martin J. Lyons         Vice President and Controller    August 10, 2005
-----------------------------   (Principal Accounting Officer)
       Martin J. Lyons


             *                            Director               August 10, 2005
----------------------------
      Susan S. Elliott


             *                            Director               August 10, 2005
----------------------------
     Gayle P.W. Jackson


             *                            Director               August 10, 2005
----------------------------
      James C. Johnson


             *                            Director               August 10, 2005
----------------------------
      Richard A. Liddy


             *                            Director               August 10, 2005
----------------------------
      Gordon R. Lohman


             *                            Director               August 10, 2005
----------------------------
     Richard A. Lumpkin


                                      II-8



          SIGNATURE                        TITLE                      DATE
          ---------                        -----                      ----

             *                            Director               August 10, 2005
----------------------------
     Charles W. Mueller


             *                            Director               August 10, 2005
----------------------------
    Douglas R. Oberhelman


             *                            Director               August 10, 2005
----------------------------
       Harvey Saligman


             *                            Director               August 10, 2005
----------------------------
      Patrick T. Stokes


* By:  /s/ Warner L. Baxter
      ----------------------
         Warner L. Baxter
         Attorney-in-Fact


                                      II-9



     THE PLAN. Pursuant to the requirements of the Securities Act of 1933, the
person who administers the undersigned employee benefit plan has duly caused
this Registration Statement to be signed on its behalf by the undersigned
thereunto duly authorized, in the City of St. Louis and State of Missouri, on
the 10th day of August, 2005.

                                     AMEREN CORPORATION EMPLOYEE LONG-TERM
                                     SAVINGS PLAN - IBEW NO. 702


                                     BY: AMEREN SERVICES COMPANY (ADMINISTRATOR)


                                     By:         /s/ Jerre E. Birdsong
                                         ---------------------------------------
                                                   Jerre E. Birdsong
                                              Vice President and Treasurer


                                     II-10



                                  EXHIBIT INDEX


**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, 1997 (1998 Form 10-K, Exhibit 3(i), File No. 1-14756).

**4.3     By-laws of the Company as amended February 13, 2004 (Exhibit 4.3, File
          No. 333-112823).

**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, File No. 1-14756).

*5        Opinion of Steven R. Sullivan, Esq., Senior Vice President, General
          Counsel and Secretary of the Company, regarding the legality of the
          securities.

*23.1     Consent of Steven R. Sullivan, Esq. (included in opinion, attached
          hereto as Exhibit 5).

*23.2     Consent of independent registered public accounting firm.

*24       Power of Attorney.

-----------
*    Filed herewith.

**   Incorporated herein by reference as indicated.