Filed by Exelon Corporation

Pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to Rule 14a-12 of the Securities Exchange Act of 1934

Subject Company: Constellation Energy Group, Inc.

(Reg. No. 333-175162)

On August 2, 2011, Exelon Corporation presented the following slides regarding the proposed merger at a meeting of its suppliers:

Creating Value Through a Strategic Merger

Exelon/Constellation merger delivers financial benefits to both

sets of shareholders

Increases scale and scope of the business across the value   

chain

Matches the industry’s premier clean merchant generating

fleet with the leading retail and wholesale customer platform

Diversifies the generation portfolio

Maintains a strong regulated earnings profile with large urban

utilities

Merger is on track to close in Q1 2012

•

$35 Billion market value

•

35,671 megawatts

•

6.6 million customers

•

44 states and D.C.

Combination will result in

enhanced scale, scope,

flexibility and financial

strength

Cautionary Statements Regarding

Forward-Looking Information

Except for the historical information contained herein, certain of the matters discussed in this communication

constitute “forward-looking statements” within the meaning of the Securities Act of 1933 and the Securities

Exchange Act of 1934, both as amended by the Private Securities Litigation Reform Act of 1995. Words such as

“may,” “will,” “anticipate,” “estimate,” “expect,” “project,” “intend,” “plan,” “believe,” “target,” “forecast,” and words

and terms of similar substance used in connection with any discussion of future plans, actions, or events identify

forward-looking statements. These forward-looking statements include, but are not limited to, statements

regarding benefits of the proposed merger of Exelon Corporation (Exelon) and Constellation Energy Group, Inc.

(Constellation), integration plans and expected synergies, the expected timing of completion of the transaction,

anticipated future financial and operating performance and results, including estimates for growth. These

statements are based on the current expectations of management of Exelon and Constellation, as applicable.

There are a number of risks and uncertainties that could cause actual results to differ materially from the

forward-looking statements included in this communication regarding the proposed merger. For example, (1) the

companies may be unable to obtain shareholder approvals required for the merger; (2) the companies may be

unable to obtain regulatory approvals required for the merger, or required regulatory approvals may delay the

merger or result in the imposition of conditions that could have a material adverse effect on the combined

company or cause the companies to abandon the merger; (3) conditions to the closing of the merger may not be

satisfied; (4) an unsolicited offer of another company to acquire assets or capital stock of Exelon or Constellation

could interfere with the merger; (5) problems may arise in successfully integrating the businesses of the

companies, which may result in the combined company not operating as effectively and efficiently as expected;

(6) the combined company may be unable to achieve cost-cutting synergies or it may take longer than expected

to achieve those synergies; (7) the merger may involve unexpected costs, unexpected liabilities or unexpected

delays, or the effects of purchase accounting may be different from the companies’ expectations; (8) the credit

ratings of the combined company or its subsidiaries may be different from what the companies expect; (9) the

businesses of the companies may suffer as a result of uncertainty surrounding the merger; (10) the companies

may not realize the values expected to be obtained for properties expected or required to be divested; (11) the

industry may be subject to future regulatory or legislative actions that could adversely affect the companies; and

(12) the companies may be adversely affected by other economic, business, and/or competitive factors. Other

unknown or unpredictable factors could also have material adverse effects on future results, performance or

achievements of Exelon or the combined company.

Cautionary Statements Regarding

Forward-Looking Information (Continued)

Discussions of some of these other important factors and assumptions are contained in Exelon’s and Constellation’s respective

filings with the Securities and Exchange Commission (SEC), and available at the SEC’s website at www.sec.gov, including: (1)

Exelon’s 2010 Annual Report on Form 10-K in (a) ITEM 1A. Risk Factors, (b) ITEM 7. Management’s Discussion and Analysis of

Financial Condition and Results of Operations and (c) ITEM 8. Financial Statements and Supplementary Data: Note 18; (2)

Exelon’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2011 in (a) Part II, Other Information, ITEM 1A.

Risk Factors, (b) Part 1, Financial Information, ITEM 2. Management’s Discussion and Analysis of Financial Condition and

Results of Operations and (c) Part I, Financial Information, ITEM 1. Financial Statements: Note 13; (3) Constellation’s 2010

Annual Report on Form 10-K in (a) ITEM 1A. Risk Factors, (b) ITEM 7. Management’s Discussion and Analysis of Financial

Condition and Results of Operations and (c) ITEM 8. Financial Statements and Supplementary Data: Note 12; and (4)

Constellation’s Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2011 in (a) Part II, Other Information,

ITEM 5.Other Information, (b) Part I, Financial Information, ITEM 2. Management’s Discussion and Analysis of Financial

Condition and Results of Operations and (c) Part I, Financial Information, ITEM 1. Financial Statements: Notes to Consolidated

Financial Statements, Commitments and Contingencies. These risks, as well as other risks associated with the proposed 

merger, are more fully discussed in the preliminary joint proxy statement/prospectus included in the Registration Statement on

Form S-4 that Exelon filed with the SEC on June 27, 2011 in connection with the proposed merger. In light of these risks,

uncertainties, assumptions and factors, the forward-looking events discussed in this communication may not occur. Readers are

cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this

communication. Neither Exelon nor Constellation undertake any obligation to publicly release any revision to its forward-looking

statements to reflect events or circumstances after the date of this communication.

Additional Information and Where to Find It

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities, or a solicitation of any

vote or approval, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be

unlawful prior to registration or qualification under the securities laws of any such jurisdiction. On June 27, 2011, Exelon filed with

the SEC a Registration Statement on Form S-4 that included a preliminary joint proxy statement/prospectus and other relevant

documents to be mailed by Exelon and Constellation to their respective security holders in connection with the proposed merger

of Exelon and Constellation.

Additional Information and Where to Find It

These materials are not yet final and may be amended.  WE URGE INVESTORS AND SECURITY HOLDERS TO READ

THE PRELIMINARY JOINT PROXY STATEMENT/PROSPECTUS AND THE DEFINITIVE JOINT PROXY

STATEMENT/PROSPECTUS AND ANY OTHER RELEVANT DOCUMENTS WHEN THEY BECOME AVAILABLE,

BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION about Exelon, Constellation and the

proposed merger.  Investors and security holders will be able to obtain these materials (when they are available) and

other documents filed with the SEC free of charge at the SEC's website, www.sec.gov.  In addition, a copy of the

preliminary joint proxy statement/prospectus and definitive joint proxy statement/prospectus (when it becomes available)

may be obtained free of charge from Exelon Corporation, Investor Relations, 10 South Dearborn Street, P.O. Box 805398,

Chicago, Illinois 60680-5398, or from Constellation Energy Group, Inc., Investor Relations, 100 Constellation Way, Suite

600C, Baltimore, MD 21202. Investors and security holders may also read and copy any reports, statements and other

information filed by Exelon, or Constellation, with the SEC, at the SEC public reference room at 100 F Street, N.E.,

Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 or visit the SEC’s website for further information on its

public reference room.

Participants in the Merger Solicitation

Exelon, Constellation, and their respective directors, executive officers and certain other members of management and

employees may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction.

Information regarding Exelon’s directors and executive officers is available in its proxy statement filed with the SEC by

Exelon on March 24, 2011 in connection with its 2011 annual meeting of shareholders, and information regarding

Constellation’s directors and executive officers is available in its proxy statement filed with the SEC by Constellation on

April 15, 2011 in connection with its 2011 annual meeting of shareholders. Other information regarding the participants in

the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, is contained

in the preliminary joint proxy statement/prospectus and will be contained in the definitive joint proxy statement/prospectus.