(As filed June 27, 2001)
                                                                File No. 70-8945

                             WASHINGTON, D.C. 20549

                        (Post-Effective Amendment No. 4)
                           APPLICATION OR DECLARATION
                                    FORM U-1
                 The Public Utility Holding Company Act of 1935


                               AMEREN CORPORATION
                              1901 Chouteau Avenue
                            St. Louis, Missouri 63103

               (Name of company or companies filing this statement
                   and address of principal executive offices)


                               AMEREN CORPORATION

                 (Name of top registered holding company parent
                         of each applicant or declarant)


                       Steven R. Sullivan, Vice President,
                          General Counsel and Secretary
                             Ameren Services Company
                              1901 Chouteau Avenue
                            St. Louis, Missouri 63103

                     (Name and address of agent for service)


              The Commission is requested to mail signed copies of
                   all orders, notices and communications to:

     Ronald Gieseke, Esq.                    William T. Baker, Jr., Esq.
     Ameren Services Company                 Thelen Reid & Priest LLP
     1901 Chouteau Avenue                    40 West 57th Street
     St. Louis, Missouri 63103               New York, New York 10019-4097

     Post-Effective Amendment No. 3, as filed in this proceeding on May 21,
2001, is hereby amended and restated in its entirety to read as follows:


     Ameren Corporation ("Ameren"), whose principal business address is at 1901
Chouteau Avenue, St. Louis, Missouri 63103, is a registered holding company
under the Public Utility Holding Company Act of 1935, as amended (the "Act").
Ameren owns all of the issued and outstanding common stock of Union Electric
Company ("AmerenUE") and Central Illinois Public Service Company ("AmerenCIPS"),
each of which is an electric and gas utility company. Together, AmerenUE and
AmerenCIPS provide retail and wholesale electric service to approximately 1.5
million customers and retail natural gas service to approximately 300,000
customers in a 24,500 square-mile area of Missouri and Illinois.

     By order dated December 30, 1997 in this proceeding (Holding Co. Act
Release No. 26809) (the "Merger Order"), the Commission authorized Ameren to
acquire AmerenUE and CIPSCO Incorporated, which was then the parent company of
AmerenCIPS, to organize a service company subsidiary, and to issue and sell
common stock pursuant to certain stock plans. In addition, the Commission
authorized Ameren to retain the direct and indirect non-utility subsidiaries and
investments of AmerenUE and CIPSCO Incorporated, subject to certain exceptions.
Specifically, the Commission conditioned its approval for the transaction on the
commitment of Ameren to reduce the voting interest or investment of Union
Electric Development Corporation ("UEDC"), a subsidiary of Union Electric, of
CIPSCO Investment Company ("CIPSCO Investment"), a subsidiary of CIPSCO
Incorporated, and of CIPSCO Venture Company ("CIPSCO Venture"), an indirect
subsidiary of CIPSCO Incorporated, in certain limited liability companies, which
are described as follows:

     St. Louis Equity Funds & Housing Missouri, Inc. - At the time of the
merger, UEDC had invested or committed to invest in varying percentages (not
greater than 23%) in ten separate investment funds (called the "St. Louis
Funds") that were formed to make investments, as a limited partner, in
individual low income housing projects in the St. Louis area. These projects
qualify for federal tax credits. Four of the ten St. Louis Funds in existence at
the time of the merger were organized as limited liability companies; the other
six are limited partnerships in which UEDC is a limited partner. In most cases,
the St. Louis Fund is the sole limited partner in an individual project
partnership. In every case, the general partner is an unaffiliated third party.
The four St. Louis Funds that were formed as limited liability companies are
so-called "manager-managed" limited liability companies, meaning that, subject
to certain limitations, the manager has full, complete and exclusive discretion
in the management and control of the business and affairs of the fund. The
manager is a not-for-profit company that is not in any way affiliated with

     Effingham Development Building II Limited Liability Company - CIPSCO
Venture holds a 40% membership interest in this entity, which owns a 267,000
square foot manufacturing facility located in the Effingham Industrial Park that


is leased to an industrial customer. This investment was intended to promote
industrial development within AmerenCIPS' service territory. Agracel Inc., an
unaffiliated third party, is the managing member.

     Mattoon Enterprise Park, LLC - CIPSCO Venture owns a 20% interest in this
limited liability company, which purchased 231 acres of farmland that was used
in the development of an industrial park within the boundaries of the City of
Mattoon. As was the case with the Effingham Industrial Park, this investment was
made to promote industrial development activity in AmerenCIPS' service territory
in order to, among other things, increase industrial load. CIPSCO Venture also
owns a one-third interest in a limited liability company, MACC, LLC, which
purchased land from Mattoon Enterprise Park, LLC and developed an industrial
facility for lease to two industrial tenants in the park as part of an
industrial development project. (This transaction closed subsequent to the date
of the Merger Order). Agracel Inc. is the managing member of both entities.

     Ameren's aggregate investment in all of these limited liability companies
is approximately $1.9 million, or less than .02% of Ameren's consolidated assets
as of December 31, 2000.

     Under Section 9(c)(3) of the Act, the Commission has authorized registered
holding companies to acquire or retain the securities of companies organized to
engage in local economic development activities.1  The Commission has
interpreted Section 9(c)(3) of the Act as preventing the creation of an
"affiliate" relationship between a registered holding company and any such
entity. Rule 40(a)(5), which exempts acquisitions of this type, is by its terms
inapplicable if the acquiring company would become an "affiliate" (i.e., owner
of 5% of more of the voting securities) of the issuer.

     Likewise, the Commission has authorized registered holding companies to
acquire or retain interests in low income housing properties that qualify for
federal tax credits. Recently, in Exelon Corporation, Holding Co. Act Release
No. 27256 (Oct. 19, 2000), the Commission articulated that such interests are
retainable if they are "passive," are made for the purpose of obtaining the tax
credits, and are "self-liquidating," i.e., the assets wind down as the tax
credits expire. Ameren's investments in low-income housing properties all meet
the standards articulated in Exelon Corporation.

     In the Merger Order, the Commission indicated that membership interests in
a limited liability company may be considered "voting securities."2
Accordingly, because Ameren's membership interest in each of the limited
liability companies that are named above exceeds 5%, the Commission conditioned
its approval of the merger upon Ameren's commitment to reduce its membership

1    See e.g., cases cited in footnotes 11 and 12 of Appendix A to the Merger

2    Merger Order, Appendix A, n. 17.


interest in each company to below 5% within three years of the date of the
Commission's order.

     By supplemental order dated December 13, 2000 (Holding Co. Act Release No.
27299), the Commission granted Ameren an extension until June 30, 2001 to comply
with its commitment to sell down its limited liability company interests. For
the reasons set forth below, Ameren is now requesting that the Commission
relieve Ameren of its commitment to sell down these limited liability company
interests and make further findings permitting Ameren to retain these interests

     Since the date of the Merger Order, the Commission has, in at least two
cases, permitted new registered holding companies to retain membership interests
greater than 5% in limited liability companies formed to develop, own and
operate low-income housing projects.3  In each case, the limited liability
companies were managed by an unaffiliated manager, and the role of the
registered holding company affiliate was "passive." Moreover, in an order dated
June 11, 2001, the Commission authorized a registered holding company to acquire
membership interests in limited liability companies formed to invest in
tax-credit low income housing projects, where the managing member is an
unaffiliated third party and the rights of the non-managing members are
equivalent to those of a limited partner in a limited partnership.4

     As in these previous cases, each of the limited liability companies in
which Ameren has an indirect interest is managed by a third-party manager that
has full authority and discretion in the management and control of the business
of each of the entities. Ameren's rights as a non-managing member in each of the
limited liability companies are substantially the same as its rights as a
limited partner in the other investment vehicles organized as limited
partnerships that it was authorized to retain.

     For the foregoing reasons, the Commission is requested to issue a further
supplemental order before June 30, 2001, permitting Ameren to retain its
indirect interest in each of the above-described limited liability companies.

3    See NiSource Inc., Holding Co. Act Release No. 27263 (Oct. 30, 2000), and
     --- -------------
     CP&L Energy, Inc., Holding Co. Act Release No. 27284 (Nov. 27, 2000). CP&L
     Energy (now Progress Energy) indirectly holds membership interests in about
     20 low-income housing ventures organized as limited liability companies. In
     most cases, it holds a 99% interest as the sole non-managing member.
     Likewise, CP&L Energy was authorized to retain membership interests of 49%
     and 33-1/3% in two limited liability companies that were organized to build
     and lease or sell buildings in industrial parks as part of its economic
     development activities.

4    See Alliant Energy Corporation, et al., Holding Co. Act Release No. 27418.
     --- ---------------------------------



     The fees, commissions and expenses paid or incurred in connection with this
Post-Effective Amendment are estimated at not more than $5,000.


     Section 9(c)(3) of the Act is applicable to the proposed transaction.

     The proposal contained herein is also subject to Rule 54. Rule 54 provides
that the Commission shall not consider the effect of the capitalization or
earnings of any subsidiary of a registered holding company that is an "exempt
wholesale generator" ("EWG") or "foreign utility company" ("FUCO") in
determining whether to approve other proposals if Rule 53(a), (b) and (c) are
satisfied. These standards are met.

     Rule 53(a)(1): Ameren's "aggregate investment" in EWGs is approximately
$262,500,000, or approximately 16.5% of Ameren's average "consolidated retained
earnings" for the four quarters ended March 31, 2001. Ameren does not currently
hold an interest in any FUCO.

     Rule 53(a)(2): Ameren will maintain books and records enabling it to
identify investments in and earnings from each EWG and FUCO in which it directly
or indirectly acquires and holds an interest. Ameren will cause each domestic
EWG in which it acquires and holds an interest, and each foreign EWG and FUCO
that is a majority-owned subsidiary, to maintain its books and records and
prepare its financial statements in conformity with U.S. generally accepted
accounting principles ("GAAP"). All of such books and records and financial
statements will be made available to the Commission, in English, upon request.

     Rule 53(a)(3): No more than 2% of the employees of Ameren's domestic
utility subsidiaries will, at any one time, directly or indirectly, render
services to EWGs and FUCOs.

     Rule 53(a)(4): Ameren will submit a copy of each Application/Declaration
relating to EWGs and FUCOs and each amendment thereto, and will submit copies of
any Rule 24 certificates required hereunder, as well as a copy of Ameren's Form
U5S, to each of the public service commissions having jurisdiction over the
retail rates of Ameren's domestic utility subsidiaries.

     In addition, Ameren states that the provisions of Rule 53(a) are not made
inapplicable to the authorization herein requested by reason of the occurrence
or continuance of any of the circumstances specified in Rule 53(b). Rule 53(c)
is inapplicable by its terms.



     No state commission and no federal commission, other than this Commission,
has jurisdiction over the matters contained herein.


     Ameren requests that the Commission's order be issued as soon as the rules
allow, and that there should not be a 30-day waiting period between issuance of
the Commission's order and the date on which the order is to become effective.
Ameren hereby waives a recommended decision by a hearing officer or any other
responsible officer of the Commission and consents to the Division of Investment
Management assisting in the preparation of the Commission's decision and/or
order, unless such Division opposes the matters proposed herein.


     The following additional exhibit is included with this filing:

     F    -    Opinion of Counsel.


     Pursuant to the requirements of the Public Utility Holding Company Act of
1935, as amended, the undersigned company has duly caused this Post-Effective
Amendment filed herein to be signed on its behalf by the undersigned thereunto
duly authorized.

                                        AMEREN CORPORATION

                                        By: /s/ Steven R. Sullivan
                                        Name:   Steven R. Sullivan
                                        Title:  Vice President, General Counsel
                                                and Secretary

Date:  June 27, 2001