Exhibit 99.1

                                                            One Ameren Plaza
                                                            1901 Chouteau
                                                            Avenue
                                                            St. Louis, MO 63103
[GRAPHIC OMITTED][GRAPHIC OMITTED]

Contact:
- -------

Media                         Analysts                        Investors
Tim Fox                       Bruce Steinke                   Investor Services
(314) 554-3120                (314) 554-2574                  (800) 255-2237
tfox2@ameren.com              bsteinke@ameren.com             invest@ameren.com
                              -------------------

FOR IMMEDIATE RELEASE
- ---------------------


                   AMEREN REPORTS THIRD QUARTER 2004 EARNINGS
                         Narrows 2004 Earnings Guidance

     St.  Louis,  Mo.,  Oct. 22,  2004---Ameren  Corporation  (NYSE:  AEE) today
announced  third  quarter 2004 net income of $232  million,  or $1.20 per share,
compared to third quarter 2003 net income of $275  million,  or $1.70 per share.
Net  income in the third  quarter  of 2003  included  an  after-tax  gain of $31
million,  or 19 cents per share,  related to the  settlement  of a dispute  over
certain coal mine reclamation issues with a supplier. Excluding this item, third
quarter 2003 net income was $244 million, or $1.51 per share. Earnings per share
for the three months ended Sept. 30, 2004,  were lower than the year-ago  period
primarily due to abnormally  mild summer weather this quarter and greater common
shares  outstanding  resulting  from the equity  financing of the Illinois Power
acquisition prior to the close of that transaction.

     Net income for the first nine months of 2004 was $447 million, or $2.44 per
share, compared to $486 million, or $3.02 per share, in the first nine months of
2003.  Net income for the first nine months of 2003 also  included the coal mine
reclamation  settlement gain along with an after-tax gain of $18 million,  or 11
cents per share, that was recorded in the first quarter of 2003 for the adoption
of a new accounting  standard  related to the  recognition  of asset  retirement
obligations.  Excluding these two gains, net income for the first nine months of
2003 was $437 million, or $2.72 per share.

     "Our solid  operational  performance  this quarter was  overshadowed by the
extremely mild summer weather  conditions  that we  experienced,"  noted Gary L.
Rainwater,   chairman,   chief   executive   officer  and  president  of  Ameren
Corporation.  "As a result, demand for power was significantly lower than during
2003's near-normal summer weather  conditions,  which negatively  impacted third
quarter 2004  earnings per share by an estimated 20 cents,  as compared to 2003.
Year-over-year  earnings per share for the quarter were also reduced by 18 cents
due to increased  shares  outstanding.  In July, the company issued 10.9 million
common shares, in

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addition to the 19.1 million  shares it issued in February 2004, to complete the
equity financing  necessary for the Illinois Power acquisition,  which closed on
Sept. 30, 2004."

     Revenues  in the third  quarter  of 2004  decreased  $36  million  to $1.32
billion,  compared  to the same  period in 2003.  Weather-sensitive  residential
electric sales decreased approximately 9 percent in the current quarter from the
third quarter of 2003 as cooling  degree days in Ameren's  service  territory in
2004 were over 20  percent  below the third  quarter of 2003.  According  to the
National Weather Service,  summer weather in Ameren's service  territory was the
7th mildest in the past 109 years,  and Ameren's  Midwest region was the coolest
in the continental U.S. in 2004.

     Weather-sensitive  commercial  electric  sales in the third quarter of 2004
were  generally  flat with the same period in 2003.  Industrial  electric  sales
decreased  approximately 4 percent,  or $7 million, in the third quarter of 2004
as compared to the third quarter of 2003,  due to the  expiration of several low
margin  power  contracts  with  customers   outside  of  Ameren's  core  service
territory.

     As a result of increased  availability  of low-cost  generation  due to the
milder weather and solid power plant operations,  interchange  electric sales in
the third quarter of 2004 increased approximately 19 percent from the comparable
2003 period.  Interchange  revenues increased  approximately 27 percent,  or $17
million,  due to the increased  sales and higher power prices as compared to the
year-ago period.

     On Sept. 30, 2004, Ameren completed the acquisition of Decatur,  Ill.-based
Illinois Power Company (IP) and a 20 percent interest in Electric  Energy,  Inc.
"Clearly, one of our significant achievements for the quarter was the closing of
the Illinois Power acquisition in only eight months, well ahead of our plan. Now
that the acquisition is completed,  we are focusing our attention on integrating
IP with the rest of our  operations to realize the expected  synergies from this
transaction, and we are executing our plan to improve IP's financial condition,"
added  Rainwater.   "We  were  also  pleased  that  immediately   following  the
announcement of the completion of the transaction, the three major credit rating
agencies increased IP's credit ratings to investment grade."

     "Since we announced this acquisition,  we have identified greater synergies
and are realizing lower financing costs than expected,"  added Warner L. Baxter,
executive  vice  president  and  chief  financial  officer  of  Ameren.   "These
incremental  benefits  have been largely  offset by  higher-than-expected  power
supply costs, including those to be recognized under purchase

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accounting,  due to  increases  in  power  prices.  The  bottom  line is that we
continue to expect the IP  acquisition  to be  accretive  to earnings by 5 to 10
cents per share in each of the first two years after  closing,  in line with our
original expectations."

     Ameren also announced today that the company was narrowing its guidance for
2004  earnings  to  between  $2.70 and $2.85 per share to  reflect  year-to-date
results, including the much milder-than-normal weather through September and the
benefit  of  the  earlier  than  expected   completion  of  the  Illinois  Power
acquisition.  The company's  guidance is subject to, among other  things,  plant
operations,  weather conditions, energy market and economic conditions,  unusual
or  otherwise  unexpected  gains or  losses  and other  risks and  uncertainties
outlined in the company's Forward-looking Statements section of this release.

     Ameren has historically  included a balance sheet, and income and cash flow
statements with its quarterly earnings releases.  As a result of the acquisition
of IP on September 30, 2004, and the need to complete the preliminary accounting
for this transaction,  Ameren is only providing a consolidated  income statement
and selected other  financial data at this time.  Ameren will file its cash flow
statement and balance sheet in its Quarterly Report on Form 10-Q for the quarter
ended Sept. 30, 2004, which will be filed by Nov. 9, 2004. Ameren will also file
a separate  Quarterly  Report on Form 10-Q for the quarter ended Sept. 30, 2004,
for Illinois Power.

     Ameren will conduct a conference  call for financial  analysts at 9:00 a.m.
(Central  Time) on Friday,  October  22,  2004,  to discuss  third  quarter  and
year-to-date 2004 earnings and other matters related to the company.  Investors,
the news media and the public may  listen to a live  Internet  broadcast  of the
Ameren analyst call at www.ameren.com by clicking on "Q3 2004 Ameren Corporation
Earnings Conference Call," then the appropriate audio link. A slide presentation
is also  available  on  Ameren's  Web site that  reconciles  earnings  per share
between the third  quarter and first nine months of 2004 and the same periods of
2003,  and provides a summary of Ameren's  updated 2004  earnings  guidance.  To
access this  presentation,  simply  follow the links for the  Webcast,  and then
click on the link for the presentation,  which is provided in a .pdf format. The
analyst  call will also be  available  for replay on the  Internet for one year.
Telephone  playback of the conference  call will also be available  beginning at
12:00 p.m.  (Central  Time),  Oct.  22,  until Oct.  29 by dialing,  U.S.  (888)
203-1112; international (719) 457-0820, and entering the number: 997214.


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     Ameren  president,  chairman and chief executive  officer Gary L. Rainwater
and executive vice president and chief  financial  officer Warner L. Baxter will
give a presentation to analysts on Tuesday, Oct. 26, 2004 at the Edison Electric
Institute 39th Annual Financial  Conference.  The presentation  will be at 12:45
p.m.  Eastern Time (11:45 a.m.  Central  Time,  9:45 a.m.  Pacific  Time).  This
presentation is being webcast and can be accessed at  www.ameren.com by clicking
on "Ameren Corporation at 39th Edison Electric Institute Financial  Conference,"
then the appropriate audio link.

     With  assets of  approximately  $17  billion,  Ameren  serves  2.3  million
electric  customers and more than 900,000  natural gas customers in Missouri and
Illinois.  Ameren owns a diverse mix of electric generating plants strategically
located in its Midwest market with a capacity of more than 14,800 megawatts.

Regulation G
- ------------

     In addition to  presenting  results of operations  and earnings  amounts in
total,  Ameren has presented  certain  information in this news release on a per
share basis.  These per share  amounts  reflect  certain  factors that  directly
impact  Ameren's total earnings.  Ameren believes this per share  information is
useful  because it  enables  readers  to better  understand  the impact of these
factors on the company's earnings.

Forward-looking Statements
- --------------------------

     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,  we are  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 past and subsequent
securities  filings,  could  cause  actual  results  to differ  materially  from
management expectations as suggested by such "forward-looking" statements:

o    the effects of the  stipulation  and  agreement  relating  to the  AmerenUE
     Missouri  electric  excess  earnings  complaint  case and other  regulatory
     actions, including changes in regulatory policies;
o    changes in laws and other  governmental  actions,  including  monetary  and
     fiscal policies;
o    the  effects of  increased  competition  in the future due to,  among other
     things,  deregulation  of certain aspects of our business at both the state
     and federal  levels,  or the  implementation  of  deregulation,  such as in
     Illinois when current power supply contracts expire in 2006;
o    the effects of participation in the Midwest Independent System Operator;
o    the  availability of fuel for the production of  electricity,  such as coal
     and natural gas, and purchased power and natural gas for distribution,  and
     the level and  volatility  of future  market  prices for such  commodities,
     including the ability to recover any increased costs;
o    the use of financial and derivative instruments;
o    average rates for electricity in the Midwest;
o    business and economic conditions, including their impact on interest rates;
o    disruptions of the capital  markets or other events making  Ameren's access
     to necessary capital more difficult or costly;






o    the impact of the adoption of new accounting  standards and the application
     of appropriate technical accounting rules and guidance;
o    actions of ratings agencies and the effects of such actions;
o    weather conditions;
o    generation plant construction, installation and performance;
o    operation of nuclear  power  facilities,  including  planned and  unplanned
     outages, and decommissioning costs;
o    the  effects  of  strategic   initiatives,   including   acquisitions   and
     divestitures;
o    the impact of current environmental regulations on utilities and generating
     companies and the  expectation  that more  stringent  requirements  will be
     introduced over time,  which could  potentially  have a negative  financial
     effect;
o    future wages and employee  benefit costs,  including  changes in returns on
     benefit plan assets;
o    difficulties  in integrating  AmerenCILCO  and AmerenIP with Ameren's other
     businesses;
o    changes in the energy markets, environmental laws or regulations,  interest
     rates or other factors adversely  impacting  assumptions in connection with
     the CILCORP Inc. and Illinois Power acquisitions;
o    cost and availability of transmission  capacity for the energy generated by
     Ameren's generating  facilities or required to satisfy energy sales made by
     Ameren; and
o    legal and administrative proceedings.

Given  these  uncertainties,  undue  reliance  should  not be  placed  on  these
forward-looking  statements.  Except  to the  extent  required  by  the  federal
securities  laws, we undertake no  obligation  to publicly  update or revise any
forward-looking  statements,  whether  as a result  of new  information,  future
events or otherwise.

                                      # # #







                            AMEREN CORPORATION (AEE)
                        CONSOLIDATED STATEMENT OF INCOME
               (Unaudited, in millions, except per share amounts)

                                                                                     Three Months Ended        Nine Months Ended
                                                                                        September 30,             September 30,
                                                                                   ----------------------   ----------------------
                                                                                      2004        2003         2004         2003
- -----------------------------------------------------------------------------------------------------------------------------------
                                                                                                                
Operating Revenues:
- ------------------------------------------------------------------------------------------------------------------------------------
          Electric                                                                    $ 1,237     $ 1,269      $ 3,182      $ 3,101
          Gas                                                                              78          82          498          450
          Other                                                                             2           2            5            6
                                                                                      --------    --------     --------     --------
              Total operating revenues                                                  1,317       1,353        3,685        3,557


Operating Expenses:
- ------------------------------------------------------------------------------------------------------------------------------------
          Fuel and purchased power                                                        330         336          890          814
          Gas purchased for resale                                                         54          51          335          316
          Other operations and maintenance                                                307         302          956          901
          Coal contract settlement                                                          -         (51)           -          (51)
          Depreciation and amortization                                                   136         132          398          388
          Taxes other than income taxes                                                    77          83          231          238
                                                                                      --------    --------     --------     --------
              Total operating expenses                                                    904         853        2,810        2,606
                                                                                      --------    --------     --------     --------
Operating Income                                                                          413         500          875          951
- ------------------------------------------------------------------------------------------------------------------------------------

Other Income and (Deductions):
- ------------------------------------------------------------------------------------------------------------------------------------
            Miscellaneous income                                                            8           4           20           16
            Miscellaneous expense                                                          (1)         (3)          (6)         (14)
                                                                                      --------    --------     --------     --------
              Total other income and (deductions)                                           7           1           14            2
                                                                                      --------    --------     --------     --------

Interest Charges and Preferred Dividends:
- ------------------------------------------------------------------------------------------------------------------------------------
          Interest                                                                         62          69          192          204
          Preferred dividends of subsidiaries                                               3           3            8            8
                                                                                      --------    --------     --------     --------
              Net interest charges and preferred dividends                                 65          72          200          212
                                                                                      --------    --------     --------     --------

Income Before Income Taxes and Cumulative Effect of Change in Accounting Principle        355         429          689          741
- ------------------------------------------------------------------------------------------------------------------------------------

Income Taxes                                                                              123         154          242          273
                                                                                      --------    --------     --------     --------
Income Before Cumulative Effect of Change in Accounting Principle                         232         275          447          468
- ------------------------------------------------------------------------------------------------------------------------------------

Cumulative Effect of Change in Accounting Principle, Net of Income Taxes                    -           -            -           18
- ------------------------------------------------------------------------------------------------------------------------------------

Net Income                                                                            $   232     $   275      $   447      $   486
====================================================================================================================================

Earnings per Common Share - Basic and Diluted:
 Income before cumulative effect of change in accounting principle                    $  1.20     $  1.70      $  2.44      $  2.91
 Cumulative effect of change in accounting principle, net of income taxes                   -           -            -         0.11
                                                                                      --------    --------     --------     --------
Earnings per Common Share - Basic and Diluted:                                        $  1.20     $  1.70      $  2.44      $  3.02
====================================================================================================================================


Average Common Shares Outstanding                                                       193.5       161.8        183.5        160.7
====================================================================================================================================








                            AMEREN CORPORATION (AEE)
                        CONSOLIDATED OPERATING STATISTICS

                                                           Three Months Ended                  Nine Months Ended
                                                              September 30,                       September 30,
                                                  -------------------------------     ------------------------------
                                                            2004             2003              2004             2003
                                                  --------------    -------------     -------------    -------------
                                                                                        
Electric Sales - KWH (in millions):
       Residential                                        5,002            5,488            13,930           13,706
       Commercial                                         5,354            5,370            15,050           14,493
       Industrial                                         4,445            4,628            13,216           12,854
       Wholesale                                          2,457            2,418             7,143            6,671
       Other                                                 80               74               235              225
                                                  --------------    -------------     -------------    -------------
         Native                                          17,338           17,978            49,574           47,949
       Interchange sales                                  2,557            2,145             7,058            6,566
       EEI (outside sales)                                1,569            1,849             3,676            4,073
                                                  --------------    -------------     -------------    -------------
         Total                                           21,464           21,972            60,308           58,588

Electric Revenues - (in millions):
       Residential                                     $    408         $    452          $  1,006         $  1,007
       Commercial                                           368              372               925              911
       Industrial                                           206              213               560              541
       Wholesale                                             92               87               256              228
       Other                                                  7                7                20               16
                                                  --------------    -------------     -------------    -------------
         Native                                           1,081            1,131             2,767            2,703
       Interchange sales                                     80               63               238              221
       EEI (outside sales)                                   40               51                87              111
       Other                                                 36               24                90               66
                                                  --------------    -------------     -------------    -------------
         Total                                            1,237            1,269             3,182            3,101

Power Supply  (%):
       Fossil                                              80.3             77.0              81.0             77.2
       Nuclear                                             11.6             11.0               8.3             11.9
       Hydro                                                1.3              0.6               1.6              0.9
       Purchased                                            6.8             11.4               9.1             10.0

Fuel Cost per KWH (cents)                                 1.098            1.166             1.104            1.081
Gas Sales - MMBTU (in thousands)                          6,467            6,983            53,817           50,745

                                                  September 30,     December 31,
                                                           2004             2003
                                                  --------------    -------------
Common Stock:
       Shares outstanding (in millions)                   194.7            162.9
       Book value per share                              $29.95           $26.73

Capitalization Ratios (a):
       Common equity                                      49.1%            47.5%
       Preferred stock                                     1.8%             2.0%
       Debt, net of cash                                  49.1%            50.5%


(a)    Includes estimated impact of Illinois Power acquisition.