Exhibit 99.1

Contacts

For Immediate Release

Ameren Announces Third Quarter 2010 Results

ST. LOUIS, MO., Oct. 29, 2010—Ameren Corporation (NYSE: AEE) today announced a third quarter 2010 net loss in accordance with generally accepted accounting principles (GAAP) of $167 million, or 70 cents per share, compared to third quarter 2009 GAAP net income of $227 million, or $1.04 per share. Excluding certain items in each year discussed below, Ameren recorded third quarter 2010 core (non-GAAP) net income of $333 million, or $1.40 per share, compared to third quarter 2009 core (non-GAAP) net income of $255 million, or $1.16 per share.

Factors favorably affecting third quarter 2010 results, compared to third quarter 2009 results, included higher electricity sales, which benefited from warmer summer weather, and new utility rates. An offsetting factor was reduced merchant generation margins, as a result of lower realized power prices and higher fuel and related transportation costs. An increased number of average common shares outstanding in 2010 also reduced per share results on a comparative basis.

“Third quarter core earnings were strong, reflecting increased electricity sales and continued disciplined cost management at each of our businesses,” said Thomas R. Voss, chairman, president and chief executive officer of Ameren Corporation. “In addition, our operating performance was solid with good generating plant availability in the quarter and year-to-date safety statistics that remain on a positive trend. As a result, we now expect 2010 core earnings to be in the range of $2.60 to $2.80 per share, an increase from our prior guidance range of $2.50 to $2.80 per share.”

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Kilowatthour (KWh) sales of electricity to native load utility customers increased 16% in the third quarter of 2010, compared to KWh sales in the third quarter of 2009. The higher KWh sales reflected warmer summer weather, a recovering economy and the return to full capacity, in March 2010, of a large customer’s aluminum smelter plant. KWh sales to industrial customers rose 18%. Excluding KWh sales to the smelter plant, industrial KWh sales increased 10%. KWh sales to residential customers rose 28%, and KWh sales to commercial customers rose 11%.

The following items were excluded from third quarter 2010 and third quarter 2009 core (non-GAAP) earnings, as applicable:

Net income in accordance with GAAP for the nine months ended Sept. 30, 2010, was $87 million, or 37 cents per share, compared to $533 million, or $2.48 per share, for the comparable period in 2009. Excluding certain items in each year, Ameren recorded nine-month 2010 core (non-GAAP) net income of $601 million, or $2.53 per share, compared to nine-month 2009 core (non-GAAP) net income of $530 million, or $2.46 per share. A reconciliation of GAAP to core (non-GAAP) earnings per share follows:

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2010 Earnings Guidance

Ameren raised its guidance for 2010 core (non-GAAP) earnings to reflect year-to-date results. Core (non-GAAP) earnings for 2010 are now expected to be in the range of $2.60 to $2.80 per share, compared to the prior range of $2.50 to $2.80 per share. GAAP earnings for 2010 are now expected to be in the range of 44 cents to 64 cents per share, compared to the prior range of $2.50 to $2.80 per share. The reduced GAAP earnings guidance primarily reflects the non-cash goodwill and other asset impairment charges recorded in the third quarter of 2010. The 2010 core (non-GAAP) earnings guidance excludes a $0.06 per share charge related to the deferred tax impact of new federal healthcare laws and a $2.19 per share charge related to goodwill and other asset impairments associated with the merchant generation business. Any net unrealized mark-to-market gains or losses in the fourth quarter of 2010 will impact GAAP earnings but are excluded from GAAP and core (non-GAAP) earnings guidance because the company is unable to reasonably estimate the impact of any such gains or losses.

Ameren expects its business segments to provide the following contributions to 2010 core (non-GAAP) earnings per share:

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Ameren’s earnings guidance for 2010 assumes normal weather for the fourth quarter of the year and is subject to the effects of, among other things, regulatory decisions and legislative actions, plant operations, energy and capital and credit market conditions, economic conditions, severe storms, unusual or otherwise unexpected gains or losses, and other risks and uncertainties outlined, or referred to, in the Forward-looking Statements section of this press release.

Ameren Missouri Earnings

Core (non-GAAP) earnings for Ameren Missouri, the company’s Missouri regulated operations, were $221 million in the third quarter of 2010, compared to $145 million in the third quarter of 2009. The improvement in core (non-GAAP) earnings was primarily due to a 12% increase in electricity sales to native load customers, as a result of warmer summer weather, a recovering economy and the return to full capacity in, March 2010, of the segment’s largest customer, the Noranda Aluminum smelter plant. New electric rates, effective June 21, 2010, and higher capitalization of financing costs for construction projects also contributed to the earnings improvement. The impact of these positive factors was reduced by higher plant operations and maintenance expenses, among other items. GAAP earnings were $223 million in the third quarter of 2010 versus $141 million in the third quarter of 2009. The GAAP earnings comparison was impacted by the factors mentioned above and by employee separation and other charges in the third quarter of 2009.

Ameren Illinois Earnings

Core (non-GAAP) earnings for Ameren Illinois, the company’s Illinois regulated operations, were $89 million in the third quarter of 2010, compared to $62 million in the third quarter of 2009. The improvement in core (non-GAAP) earnings was primarily due to a 19% increase in electricity sales as a result of warmer summer weather and a recovering economy. Adjustments to energy delivery rates, effective in Oct. 2009 (the phased portion of AmerenIP’s 2008 rate adjustment) and May 2010, also contributed to the earnings improvement. The impact of these positive factors was reduced by higher financing costs and higher taxes other than income taxes, among other items. GAAP earnings were $89 million in the third quarter of 2010 versus $59 million in the third quarter of 2009. The GAAP earnings comparison was impacted by the factors mentioned above and by charges related to the Illinois electric settlement agreement reached in 2007 and by employee separation and other charges, all recorded in the third quarter of 2009.

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Merchant Generation Earnings

Core (non-GAAP) earnings for the merchant generation operations were $34 million in the third quarter of 2010, compared to $62 million in the third quarter of 2009. The decline in core (non-GAAP) earnings was principally due to lower realized power prices and higher fuel and related transportation costs. In addition, depreciation expense increased, reflecting environmental control equipment placed in service in late 2009 and early 2010. The impact of these factors was mitigated by reduced operations and maintenance expenses. GAAP losses were $470 million in the third quarter of 2010 versus GAAP earnings of $37 million in the third quarter of 2009. The GAAP earnings comparison was impacted by the factors mentioned above and by the previously discussed non-cash goodwill and other asset impairment charges in the third quarter of 2010. These charges were mitigated by a gain in the third quarter of 2010, compared to a loss in the third quarter of 2009, from net unrealized mark-to-market activity. The GAAP earnings comparison was also impacted by employee separation and other charges, as well as a charge related to the Illinois electric settlement agreement reached in 2007, all recorded in the third quarter of 2009.

Analyst Conference Call

Ameren will conduct a conference call for financial analysts at 9:00 a.m. Central Time on Friday, Oct. 29, to discuss third quarter 2010 earnings and other matters. Investors, the news media and the public may listen to a live Internet broadcast of the call at www.ameren.com by clicking on “Q3 2010 Ameren Corporation Earnings Conference Call,” followed by the appropriate audio link. An accompanying slide presentation will be available on Ameren’s Web site. This presentation will be posted in the “Investors” section of the Web site under “Webcasts & Presentations.” The analyst call will also be available for replay on the Internet for one year. In addition, a telephone playback of the conference call will be available beginning at approximately noon Central Time, from Oct. 29 through Nov. 5, by dialing, U.S. (877) 660-6853 or international (201) 612-7415, and entering account number 352 and ID number 359132.

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Regulation G Statement

Ameren has presented certain information in this release on a diluted cents per share basis. These diluted per share amounts reflect certain factors that directly impact Ameren’s total earnings per share. The core (non-GAAP) earnings per share and core (non-GAAP) earnings per share guidance exclude one or more of the following: the earnings impact of the 2007 settlement agreement among parties in Illinois for comprehensive electric rate relief and customer assistance, employee separation and other charges, a charge for the deferred tax impact of new federal healthcare laws, charges for goodwill and other asset impairments, and net unrealized mark-to-market gains or losses. Ameren uses core (non-GAAP) earnings internally for financial planning and for analysis of performance. Ameren also uses core (non-GAAP) earnings as primary performance measurements when communicating with analysts and investors regarding our earnings results and outlook, as the company believes it allows it to more accurately compare the company’s ongoing performance across periods.

In providing consolidated and segment core (non-GAAP) earnings guidance, there could be differences between core (non-GAAP) earnings and earnings prepared in accordance with GAAP for certain items, such as those listed above. Ameren is unable to estimate the impact, if any, on future GAAP earnings of such items.

Forward-Looking Statements

Statements in this release not based on historical facts are considered “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 our filings with the SEC could cause actual results to differ materially from management expectations suggested in such forward-looking statements:

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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 update or revise publicly any forward-looking statements to reflect new information or future events.

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With assets of $24 billion, St. Louis-based Ameren Corporation owns a diverse mix of electric generating plants strategically located in our Midwest market, with a generating capacity of more than 16,900 megawatts. Through our Missouri and Illinois subsidiaries, we serve 2.4 million electric customers and nearly 1 million natural gas customers in a 64,000-square-mile area. Our mission is to meet their energy needs in a safe, reliable, efficient and environmentally responsible manner. For more information, visit Ameren.com.

AMEREN CORPORATION (AEE)

CONSOLIDATED OPERATING STATISTICS

AMEREN CORPORATION (AEE)

CONSOLIDATED OPERATING STATISTICS

AMEREN CORPORATION (AEE)

CONSOLIDATED STATEMENT OF INCOME (LOSS)

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AMEREN CORPORATION (AEE)

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AMEREN CORPORATION (AEE)

CONSOLIDATED STATEMENT OF CASH FLOWS

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