Exhibit 99.1


[GRAPHIC OMITTED][GRAPHIC OMITTED]
                                                            One Ameren Plaza
                                                            1901 Chouteau Avenue
                                                            St. Louis, MO 63103
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 SECOND QUARTER 2004 EARNINGS
                         Updates 2004 Earnings Guidance

     St.  Louis,  Mo.,  July 29,  2004---Ameren  Corporation  (NYSE:  AEE) today
announced second quarter 2004 net income of $118 million, or 65 cents per share,
compared  to second  quarter  2003 net income of $110  million,  or 68 cents per
share.  Net income for the first six months of 2004 was $215  million,  or $1.20
per share,  compared to $211 million,  or $1.32 per share,  in the first half of
2003. Net income in the first six months of last year included an after-tax gain
of $18  million,  or 11 cents per share,  due to the  adoption of an  accounting
standard related to asset retirement obligations. Income in the first six months
of 2003 before the cumulative  effect of this change in an accounting  principle
was $193 million, or $1.21 per share.

     "Despite some challenges during the second quarter this year, we once again
delivered solid  financial  results," said Gary L.  Rainwater,  chairman,  chief
executive officer and president of Ameren Corporation.  "This quarter's earnings
per share were down from the prior year due largely to the incremental  costs we
incurred in connection with the scheduled  refueling and  maintenance  outage at
our Callaway  nuclear plant. A similar Callaway outage did not occur in 2003. In
addition,  earnings per share were lower due to the equity dilution  principally
caused  by  our  issuance  of  common  shares  to  prefund  the  Illinois  Power
acquisition.  Despite these factors, second quarter earnings per share were only
modestly below the prior year as solid organic  growth,  a return to more normal
summer  weather,  stronger  power prices and our focus on cost  control  largely
offset the cost of the Callaway  outage and earnings  per share  dilution,"  Mr.
Rainwater added.

     Revenues  in the  second  quarter  of 2004  increased  $64  million to $1.2
billion,  compared  to the same  period  in 2003.  Solid  organic  growth in the
company's  service  territory  and a return to more  normal  summer  weather  as
compared to the prior year largely drove higher revenues.  In the second quarter
of 2004, cooling degree days in Ameren's service territory increased

                                    -more -




Add One

approximately  75 percent from the cooler than normal second  quarter last year.
Weather-sensitive   residential   electric  sales  increased  15  percent,   and
commercial  electric  sales  increased  6 percent in the second  quarter of 2004
versus 2003.

     Interchange  electric  revenues  also  increased  $15 million in the second
quarter of 2004, as compared to the same period in 2003, due primarily to higher
power prices. Wholesale electric revenues increased $13 million primarily due to
the addition of new customers.

     Fuel and purchased power costs rose $43 million,  and other  operations and
maintenance  expenses  increased  $36  million in the second  quarter of 2004 as
compared to the second quarter of 2003.  These increased costs were  principally
due to the Callaway nuclear plant's scheduled  refueling and maintenance  outage
in the second  quarter of 2004. A refueling  outage occurs at the Callaway plant
approximately  every 18 months and there was no refueling and maintenance outage
in 2003. This year's outage lasted 64 days and reduced quarterly  earnings by an
estimated 22 cents per share due to the incremental cost of fuel and replacement
power and higher maintenance costs.

     Operations and maintenance expenses in the second quarter of 2004 benefited
from the Federal Energy Regulatory  Commission-ordered  refund of $18 million in
exit  fees  previously  paid  to the  Midwest  Independent  Transmission  System
Operator, Inc. (MISO). Ameren rejoined the MISO on May 1, 2004.

     Ameren  continues to move towards  completion  of its proposed  acquisition
from Dynegy Inc. (NYSE: DYN) of Decatur, Ill.-based Illinois Power Company and a
20 percent interest in Electric Energy,  Inc. "We are moving through  regulatory
approvals and remain on target to close the acquisition by the end of this year,
if not sooner. Just yesterday,  we received approval of the acquisition from the
Federal  Energy  Regulatory  Commission.  In addition,  we already have received
approval from the Federal Communications Commission and the waiting period under
the  Hart-Scott-Rodino Act has expired. The acquisition must also be approved by
the Illinois  Commerce  Commission and the Securities and Exchange  Commission,"
noted Rainwater.

     In early July,  Ameren sold 10.9 million new common shares,  generating net
proceeds of $445 million.  "The proceeds from this offering,  when combined with
the $853  million of  proceeds  generated  by our  February  2004  common  stock
offering,  completes our equity  financing for the Illinois Power  acquisition,"
added Warner L. Baxter,  executive vice president and chief financial officer of
Ameren.




                                    -more -

Add Two

     Dilution and financing costs,  principally resulting from additional common
shares issued in the February offering, reduced earnings by an estimated 6 cents
per share in the second  quarter,  and 9 cents per share in the first six months
of 2004.  Dilution was caused by shares being issued prior to the  completion of
the Illinois Power acquisition.  Based on current assumptions,  the acquisition,
once  completed,  is expected to be  accretive  to earnings by 5 to 10 cents per
share in each of the first two years after the closing of that  transaction  and
is  expected  to  provide  significant,  long-term  value  for  all of  Ameren's
stakeholders.

     Due to the  expected  additional  earnings  dilution for the second half of
2004 of  approximately  8 cents per share from the July common  stock  offering,
Ameren  announced  today that the company is  adjusting  its 2004  guidance  for
earnings  per share to  between  $2.70 and $2.90 per  share.  The 2004  estimate
includes the impact of common  shares  issued in February and early July to fund
the Illinois  Power  acquisition,  but excludes any  potential  earnings  impact
resulting from 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 will conduct a conference  call for financial  analysts at 9:00 a.m.
(Central Time) on Thursday,  July 29, to discuss second quarter and year to date
2004 earnings and other  matters  relating 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 "Q2 2004  Earnings  Conference
Call," then the appropriate  audio link. A slide  presentation is also available
on  Ameren's  website  that  reconciles  earnings  per share  between the second
quarter and first six months of 2003 and the same periods of 2004,  and provides
a summary of Ameren's  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),
July 29, until August 5 by dialing,  U.S. (800)  428-6051;  international  (973)
709-2089, and entering the number: 366596.

     With  assets  of $14.7  billion,  Ameren  owns a  diverse  mix of  electric
generating plants strategically located in its Midwest market with a capacity of
more than 14,600  megawatts.  Ameren serves 1.7 million  electric  customers and
500,000  natural gas  customers  in a 49,000  square-mile  area of Missouri  and
Illinois.




                                     -more-

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, the company 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 past and subsequent
filings with the Securities and Exchange Commission,  could cause actual results
to  differ  materially  from  management   expectations  as  suggested  by  such
"forward-looking" statements:

o    the closing and timing of Ameren's  acquisition  of Illinois  Power and the
     impact of any  conditions  imposed by regulators  in connection  with their
     approval thereof;
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 impact on the company of current regulations related to the opportunity
     for customers to choose alternative energy suppliers in Illinois;
o    the  effects of  increased  competition  in the future due to,  among other
     things,  deregulation of certain aspects of the company's  business at both
     the state and federal levels;
o    the   effects   of   participation   in   a   Federal   Energy   Regulatory
     Commission-approved    regional   transmission   organization,    including
     activities associated with 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;
o    the impact of the adoption of new accounting  standards and the application
     of appropriate technical accounting rules and guidance;
o    interest rates and the availability of capital;
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  benefits costs,  including changes in returns on
     benefit plan assets;
o    disruptions  of the capital  markets or other events  making the  company's
     access to necessary capital more difficult or costly;
o    competition from other generating facilities, including new facilities that
     may be developed;
o    difficulties in integrating AmerenCILCO and Illinois Power, if consummated,
     with the company'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 and Illinois Power (if consummated) acquisitions;
o    cost and availability of transmission  capacity for the energy generated by
     the company's  generating  facilities  or required to satisfy  energy sales
     made by the company; and
o    legal and administrative proceedings.

                                      # # #









                            AMEREN CORPORATION (AEE)
                        CONSOLIDATED OPERATING STATISTICS

                                                         Three Months Ended                   Six Months Ended
                                                              June 30,                            June 30,
                                                  -----------------------------       -----------------------------
                                                          2004             2003              2004             2003
                                                  ------------     ------------       ------------       ----------
                                                                                       
Electric Sales - KWH (in millions):
       Residential                                      3,984            3,469              8,927            8,219
       Commercial                                       4,877            4,600              9,696            9,124
       Industrial                                       4,448            4,438              8,771            8,226
       Wholesale                                        2,197            1,967              4,687            4,253
       Other                                               73               70                157              148
                                                  ------------     ------------       ------------       ----------
         Native                                        15,579           14,544             32,238           29,970
       Interchange sales                                2,077            2,000              4,501            4,421
       EEI (outside sales)                              1,229            1,456              2,106            2,225
                                                  ------------     ------------       ------------       ----------
         Total                                         18,885           18,000             38,845           36,616

Electric Revenues - (in millions):
       Residential                                $       312      $       281        $       598        $     555
       Commercial                                         316              302                557              529
       Industrial                                         190              192                354              327
       Wholesale                                           79               66                164              141
       Other                                                6                6                 13               12
                                                  ------------     ------------       ------------       ----------
         Native                                           903              847              1,686            1,564
       Interchange sales                                   72               57                157              158
       EEI (outside sales)                                 31               42                 47               60
       Other                                               26               22                 55               42
                                                  ------------     ------------       ------------       ----------
         Total                                          1,032              968              1,945            1,824

Power Supply  (%):
    Fossil                                               83.9             73.8               81.4             77.3
    Nuclear                                               3.1             13.3                6.5             12.4
    Hydro                                                 1.8              1.5                1.7              1.1
    Purchased                                            11.2             11.4               10.4              9.2

Fuel Cost per KWH (cents)                               1.142            1.074              1.108            1.030
Gas Sales - MMBTU (in thousands)                       12,314           16,697             47,350           43,762


                                                      June 30,     December 31,
                                                          2004             2003
                                                  ------------     -------------
Common Stock:
       Shares outstanding (in millions)                 183.3            162.9
       Book value per share                       $     28.58      $     26.73

Capitalization Ratios:
       Common equity                                     56.3%            47.5%
       Preferred stock                                    2.0%             2.0%
       Debt, net of cash                                 41.7%            50.5%







                            AMEREN CORPORATION (AEE)
                           CONSOLIDATED BALANCE SHEET
                            (Unaudited, in millions)

                                                                           June 30,           December 31,
                                                                            2004                 2003
- -----------------------------------------------------------------------------------------------------------

                      ASSETS
- -----------------------------------------------------------------------------------------------------------
                                                                                

Current Assets:
        Cash and cash equivalents                                    $             511    $            111
        Accounts receivable - trade                                                343                 326
        Unbilled revenue                                                           258                 221
        Miscellaneous accounts and notes receivable                                 47                 126
        Materials and supplies, at average cost                                    458                 487
        Other current assets                                                        35                  46
                                                                     ------------------   -----------------
         Total current assets                                                    1,652               1,317
                                                                     ------------------   -----------------
Property and Plant, Net                                                         11,052              10,920
Investments and Other Non-Current Assets:
        Investments in leveraged leases                                            153                 164
        Nuclear decommissioning trust fund                                         220                 212
        Goodwill and other intangibles, net                                        565                 574
        Other assets                                                               353                 320
                                                                     ------------------   -----------------
         Total investments and other assets                                      1,291               1,270
                                                                     ------------------   -----------------
Regulatory Assets                                                                  682                 729
- -----------------------------------------------------------------------------------------------------------
TOTAL ASSETS                                                         $          14,677    $         14,236
===========================================================================================================

       LIABILITIES AND STOCKHOLDERS' EQUITY
- -----------------------------------------------------------------------------------------------------------
Current Liabilities:
        Current maturities of long-term debt                         $             291    $            498
        Short-term debt                                                             35                 161
        Accounts and wages payable                                                 273                 480
        Taxes accrued                                                              220                 103
        Other current liabilities                                                  215                 215
                                                                     ------------------   -----------------
         Total current liabilities                                               1,034               1,457
                                                                     ------------------   -----------------
Long-term Debt, Net                                                              4,051               4,070
Preferred Stock Subject to Mandatory Redemption                                     21                  21
Deferred Credits and Other Non-Current Liabilities:
        Accumulated deferred income taxes, net                                   1,775               1,853
        Accumulated deferred investment tax credits                                145                 151
        Regulatory liabilities                                                     862                 824
        Asset retirement obligations                                               425                 413
        Accrued pension and other post-retirement benefits                         744                 699
        Other deferred credits and liabilities                                     175                 190
                                                                     ------------------   -----------------
         Total deferred credits and other liabilities                            4,126               4,130
                                                                     ------------------   -----------------
Preferred Stock Not Subject to Mandatory Redemption                                182                 182
Minority Interest in Consolidated Subsidiaries                                      25                  22
Stockholders' Equity:
        Common stock                                                                 2                   2
        Other paid-in capital, principally premium on common stock               3,456               2,552
        Retained earnings                                                        1,835               1,853
        Accumulated other comprehensive income (loss)                              (41)                (44)
        Other                                                                      (14)                 (9)
                                                                     ------------------   -----------------
         Total stockholders' equity                                              5,238               4,354
- -----------------------------------------------------------------------------------------------------------

TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY                           $          14,677    $         14,236
===========================================================================================================








                              AMEREN CORPORATION (AEE)
                           CONSOLIDATED STATEMENT OF INCOME
                  (Unaudited, in millions, except per share amounts)
                                                                                   Three Months Ended        Six Months Ended
                                                                                         June 30,                 June 30,
                                                                                ----------------------     -----------------------
                                                                                   2004         2003           2004        2003
- ----------------------------------------------------------------------------------------------------------------------------------
                                                                                                     

Operating Revenues:
           Electric                                                             $ 1 ,032     $    968      $  1,945     $  1,824
           Gas                                                                       119          118           420          368
           Other                                                                       1            2             3            4
                                                                                ---------    ---------     ---------    ---------
               Total operating revenues                                            1,152        1,088         2,368        2,196

Operating Expenses:
- ----------------------------------------------------------------------------------------------------------------------------------
           Fuel and purchased power                                                  282          239           553          471
           Gas purchased for resale                                                   75           83           288          264
           Other operations and maintenance                                          343          307           649          599
           Depreciation and amortization                                             132          132           262          256
           Taxes other than income taxes                                              74           77           154          155
                                                                                ---------    ---------     ---------    ---------
               Total operating expenses                                              906          838         1,906        1,745
                                                                                ---------    ---------     ---------    ---------
Operating Income                                                                     246          250           462          451
- ----------------------------------------------------------------------------------------------------------------------------------

Other Income and (Deductions):
- ----------------------------------------------------------------------------------------------------------------------------------
           Miscellaneous income                                                        4            5            12           11
           Miscellaneous expense                                                      (4)          (7)           (5)         (10)
                                                                                ---------    ---------     ---------    ---------
               Total other income and (deductions)                                     -           (2)            7            1
                                                                                ---------    ---------     ---------    ---------
Interest Charges and Preferred Dividends:
- ----------------------------------------------------------------------------------------------------------------------------------
           Interest                                                                   66           69           130          135
           Preferred dividends of subsidiaries                                         2            2             5            5
                                                                                ---------    ---------     ---------    ---------
               Net interest charges and preferred dividends                           68           71           135          140
                                                                                ---------    ---------     ---------    ---------

Income Before Income Taxes and Cumulative Effect of Change in
    Accounting Principle                                                             178          177           334          312
- ----------------------------------------------------------------------------------------------------------------------------------
Income Taxes                                                                          60           67           119          119
                                                                                ---------    ---------     ---------    ---------
Income Before Cumulative Effect of Change in Accounting Principle                    118          110           215          193
- ----------------------------------------------------------------------------------------------------------------------------------

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

Net Income                                                                      $    118     $    110      $    215     $    211
==================================================================================================================================

Earnings per Common Share - Basic and Diluted:
   Income before cumulative effect of change in accounting principle            $   0.65     $   0.68      $   1.20     $   1.21
   Cumulative effect of change in accounting principle, net of income taxes            -            -             -         0.11
                                                                                ---------    ---------     ---------    ---------
Earnings per Common Share - Basic and Diluted:                                  $   0.65     $   0.68      $   1.20     $   1.32
==================================================================================================================================

Average Common Shares Outstanding                                                  182.7        161.2         178.5        160.1
==================================================================================================================================







                            AMEREN CORPORATION (AEE)
                      CONSOLIDATED STATEMENT OF CASH FLOWS
                            (Unaudited, in millions)
                                                                                                 Six Months Ended
                                                                                                      June 30,
                                                                                             -----------------------
                                                                                               2004           2003
- --------------------------------------------------------------------------------------------------------------------

Cash Flows From Operating Activities:
- --------------------------------------------------------------------------------------------------------------------
                                                                                               
   Net income                                                                                $   215        $   211
   Adjustments to reconcile net income to net cash
     provided by operating activities:
        Cumulative effect of change in accounting principle                                        -            (18)
        Depreciation and amortization                                                            262            256
        Amortization of nuclear fuel                                                              13             16
        Amortization of debt issuance costs and premium/discounts                                  5              5
        Deferred income taxes, net                                                                (5)            (9)
        Deferred investment tax credits, net                                                      (6)            (6)
        Coal contract settlement                                                                  18              -
        Changes in assets and liabilities, excluding the effects of the acquisitions:
                Receivables, net                                                                 (23)             6
                Materials and supplies                                                            29            (14)
                Accounts and wages payable                                                      (162)          (149)
                Taxes accrued                                                                    117             99
                Assets, other                                                                    (57)            17
                Liabilities, other                                                                29             27
                Other                                                                              1            (11)
                                                                                             --------       --------
Net cash provided by operating activities                                                        436            430

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

Cash Flows From Investing Activities:
- --------------------------------------------------------------------------------------------------------------------
   Construction expenditures                                                                    (379)          (332)
   Acquisitions, net of cash acquired                                                              -           (489)
   Nuclear fuel expenditures                                                                      (5)            (1)
   Other                                                                                          17              6
                                                                                             --------       --------
Net cash used in investing activities                                                           (367)          (816)

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

Cash Flows From Financing Activities:
- --------------------------------------------------------------------------------------------------------------------
   Dividends on common stock                                                                    (232)          (205)
   Capital issuance costs                                                                        (23)           (11)
   Redemptions, Repurchases and Maturities:
      Nuclear fuel lease                                                                         (67)           (20)
      Short-term debt                                                                           (126)           (91)
      Long-term debt                                                                            (260)          (420)
   Issuances:
      Common stock                                                                               935            308
      Long-term debt                                                                             104            298
                                                                                             --------       --------
Net cash provided by (used in) financing activities                                              331           (141)

- --------------------------------------------------------------------------------------------------------------------
Net Change In Cash and Cash Equivalents                                                          400           (527)
Cash and Cash Equivalents at Beginning of Year                                                   111            628
- --------------------------------------------------------------------------------------------------------------------

Cash and Cash Equivalents at End of Period                                                   $   511        $   101
====================================================================================================================