WASHINGTON, DC 20549

                                    FORM 8-K

                                 CURRENT REPORT

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

                Date of Report (Date of earliest event reported):
                                 April 29, 2002

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

        Missouri                        1-14756                  43-1723446
 (State or other jurisdiction         (Commission            (I.R.S. Employer
     of incorporation)                File Number)           Identification No.)

                 1901 Chouteau Avenue, St. Louis, Missouri 63103
              (Address of principal executive offices and Zip Code)

       Registrant's telephone number, including area code: (314) 621-3222


     On April 29, 2002, the Registrant issued a press release announcing that it
has  entered  into a  definitive  agreement  with  The AES  Corporation  for the
purchase of the common stock of its subsidiary, CILCORP Inc., the parent company
of Central  Illinois Light Company.  The press release is attached as Exhibit 99
and is incorporated herein by reference.


        (c) Exhibits.

            99  Press release, dated April 29, 2002, issued by the Registrant.


     Pursuant to the  requirements  of the Securities  Exchange Act of 1934, the
Registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned thereunto duly authorized.

                                         AMEREN CORPORATION

                                         By /s/ Warner L. Baxter
                                                Warner L. Baxter
                                            Senior Vice President, Finance
                                              (Principal Financial Officer)

Date:  April 29, 2002

                                    Exhibit Index

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

     99    - Press release dated April 29, 2002, issued by Ameren Corporation.

                                                                     EXHIBIT 99


News Release
One Ameren Plaza
1901 Chouteau Avenue
St. Louis, MO 63103


     Media:                 Analysts:                 Investors:
     Susan Gallagher        Bruce Steinke             Investor Services
     (314) 554-2175         (314) 554-2574  


     St. Louis,  Mo.,  April 29,  2002---Ameren  Corporation  (NYSE:  AEE) today
     announced  the  signing  of a  definitive  agreement  for the  purchase  of
     CILCORP,  Inc., from The AES Corporation (NYSE: AES). CILCORP is the parent
     company of Peoria-based Central Illinois Light Co. (CILCO).

          In a transaction  valued at $1.4 billion,  Ameren will assume  CILCORP
     debt at closing and pay the balance in cash to purchase the common stock of
     CILCORP,  along with certain other assets.  The purchase includes CILCORP's
     natural gas and electric  businesses,  including 1,200 megawatts of largely
     coal-fired  generating  capacity.   Upon  completion  of  the  acquisition,
     expected  within 12 months,  CILCO would become an Ameren  subsidiary,  but
     would remain a separate utility company, known as AmerenCILCO.

          With this  acquisition,  Ameren will rank as Illinois'  second largest
     electric  utility  based on the  number  of  customers,  total  assets  and
     operating revenues.

          "This  acquisition  is a  natural  fit  with our  core  energy  growth
     strategy," says Charles W. Mueller,  chairman and chief executive  officer,
     Ameren  Corporation.  "CILCORP's  operations are in a service territory and
     market where we already operate very  effectively.  In addition,  CILCORP's
     base-load generation assets,  strong customer base, and low-cost operations
     complement Ameren's existing Illinois operations  extremely well. Synergies
     from the acquisition  will make this transaction  immediately  accretive to
     earnings and will drive strong long-term growth for our company."

          "This  acquisition   brings  impressive   benefits  to  customers  and
     communities  in  Illinois,"  says Gary L.  Rainwater,  president  and chief
     operating officer of Ameren Corporation.  "We will expand our commitment of
     bringing  high-quality,  reliable  electric  and  natural  gas  services to
     CILCORP's approximately 200,000 electric and 200,000 gas customers. We take
     this  commitment  seriously,  as  evidenced  by our top ratings on customer
     service in a recent Illinois Commerce  Commission  survey."

          The transaction was unanimously  approved by both companies' boards of
     directors,  but  is  subject  to the  approval  of  the  Illinois  Commerce
     Commission,  the  Securities  and Exchange  Commission,  the Federal Energy
     Regulatory  Commission  and the  expiration of the waiting period under the
     Hart-Scott-Rodino  Act. No approval is required from shareholders of either

                                   -- more --

     Add One

     Following are key components of this transaction:

     >>   The  headquarters of AmerenCILCO  will remain in Peoria,  where Ameren
          anticipates  maintaining the existing operations center, customer call
          center,  business-to-business  and retail marketing groups, plus other
          support functions.

     >>   The  transaction  also  includes   AES-Medina  Valley  Cogen,   LLC--a
          40-megawatt,  gas-fired electric  generation plant. The plant produces
          electricity,  steam and chilled water,  which is sold to CILCO.  CILCO
          resells  plant  output  to  Caterpillar--CILCO's   largest  industrial

     >>   Electric  rates will  remain  frozen at current  levels at least until
          2004,  and existing  generation  and energy  services  contracts  with
          nonresidential customers will remain in force.

     >>   With the addition of CILCO,  Ameren expects to make very limited staff
          reductions  at  Ameren-wide,   and  those  reductions  would  be  made
          primarily through attrition. Existing labor contracts will be honored.

     >>   Ameren  plans to increase  CILCO's  annual  civic,  charitable  and
          social service  contribution  levels to at least $1 million to be used
          in the Peoria area and other locations now served by CILCO. That level
          will  allow  for  continued  support  of such  activities  and for the
          expansion  of three  Ameren  programs  into the former  CILCO  service
          territory. They are:

          o   Dollar More, a low-income energy assistance program,

          o   Power Player, a program to support youth sports teams, and

          o   SmartLights, providing installation of energy-efficient lighting
              in public areas.

     >>   Ameren  plans to commit  additional  funds  annually  in  continued
          support for economic development  organizations and to support special
          marketing programs aimed at attracting new jobs to the Peoria area.

          "Together,  Ameren and CILCORP  will  continue a heritage of providing
     strong support to hundreds of Illinois communities with a combined customer
     base of nearly 600,000 electric and nearly 400,000 natural gas customers in
     Illinois," added Rainwater.

          Ameren was advised on this transaction by Goldman, Sachs & Co.

                            CONFERENCE CALL ADVISORY:

          Ameren will conduct a conference call for financial  analysts at 10:00
     a.m.  (Central  Daylight Time). It will include a slide  presentation  that
     will be available online at

          Ameren will conduct a conference  call for media at 11:30 a.m.,  (CDT)
     on Monday,  April 29, to discuss the transaction.  All interested media may
     join the 11:30 a.m. media conference call by dialing 1-800-634-1568.

          Investors,  the news  media  and the  public  may also  listen to live
     Internet  broadcasts of both calls,  at  Web site visitors
     simply click on  "Transaction  Conference  Call  (Analyst)" or "Transaction
     Conference Call (Media)" and then click on the appropriate audio link. Both
     the  analyst  and media  calls  will also be  available  for  replay on the
     Internet for five days.

     Add Two

          Telephone  playback of the conference calls will also be available the
     afternoon  of  April  29,  and for 48 hours  thereafter  by  dialing,  U.S.
     1-800-633-8284; international 1-858-812-6440.

     o    For the analyst call, at 10:00 a.m. enter the number: 20567436.

     o    For the media call, at 11:30 a.m. enter the number: 20567451.

                                      # # #


     AMEREN CORPORATION:  A  $10-billion-asset  company based in St. Louis, Mo.,
     Ameren  Corporation  provides energy  services to 1.5 million  electric and
     300,000  natural gas  customers  over 44,500  square  miles in Illinois and
     Missouri.  Among the  nation's  top  utility  companies  in size and sales,
     Ameren's regulated  companies --- AmerenUE and AmerenCIPS -- were founded a
     century ago as Union Electric  Company and Central  Illinois Public Service
     Company,  respectively.  AmerenCIPS  generating  facilities on May 1, 2000,
     became  part  of  a  newly  created   nonregulated   company---AmerenEnergy
     Generating  Company;  this power is  marketed by a  nonregulated  affilate,
     AmerenEnergy   Marketing   Company.   Ameren   subsidiaries   also  include
     AmerenEnergy, Inc., a nonregulated energy trading company, and AmerenEnergy
     Fuels and Services,  a fuels  marketing,  trading and  management  services
     organization. Approximately 92 percent of the corporation's $4.5 billion in
     revenues flows from electric sales, with the remainder primarily from sales
     of natural gas.

     CILCORP:  With $1.8  billion in assets and 2001  revenues of $815  million,
     CILCORP,  formed  in 1985 and  headquartered  in  Peoria,  IL, is an energy
     services  company.  CILCORP's  largest  subsidiary,  CILCO,  serves 200,000
     electric  and more than  200,000  natural  gas  customers,  and  includes a
     regulated   electric  and  natural  gas  delivery  unit,  power  generation
     facilities,  and  a  retail  energy  business.  CILCO  has  been  providing
     electricity  and natural gas to customers in central  Illinois  since 1915.
     The company has four  generating  units  primarily  fueled by coal,  with a
     total capacity of over 1,200 megawatts.

                                      # # #

     Safe Harbor Statement
     Statements made in this release,  which are not based on historical  facts,
     are  "forward-looking"  and,  accordingly,  involve risks and uncertainties
     that could cause actual results to differ  materially from those discussed.
     Although such "forward-looking" statements have been made in good faith and
     are  based  on  reasonable  assumptions,  there  is no  assurance  that the
     expected  results  will be  achieved.  These  statements  include  (without
     limitation)   statements  as  to  future  expectations,   beliefs,   plans,
     strategies,  objectives,  events, conditions, and financial performance. In
     connection  with the "Safe  Harbor"  provisions  of the Private  Securities
     Litigation  Reform  Act  of  1995,  Ameren  is  providing  this  cautionary
     statement to identify  important factors that could cause actual results to
     differ  materially  from  those  anticipated.  The  following  factors,  in
     addition  to those  discussed  elsewhere  in this  release  and in Ameren's
     annual report on SEC Form 10-K for the fiscal year ended December 31, 2001,
     and subsequent securities filings, could cause results to differ materially
     from  management   expectations  as  suggested  by  such  "forward-looking"

     o    delays in receipt  of  regulatory  approvals  for the  acquisition  of
          CILCORP or unexpected adverse conditions or terms of those approvals;

     o    difficulties in integrating CILCO with Ameren's other businesses;

     o    changes in the coal  markets,  environmental  laws or  regulations  or
          other factors adversely impacting synergy assumptions; and

     o    disruptions  of the capital  markets or other events  making  Ameren's
          access to necessary capital more difficult or costly.

                                      # # #