UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

August 2, 2010

Date of Report (Date of earliest event reported)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Section 1 – Registrant’s Business and Operations

On August 2, 2010 Commonwealth Edison Company (ComEd) issued $500 million aggregate principal amount of its First Mortgage 4.00% Bonds, Series 109, due August 1, 2020. See Item 2.03 below for a description of the Bonds and related agreements.

Section 2 – Financial Information

On August 2, 2010, ComEd issued $500 million of its First Mortgage 4.00% Bonds, Series 109, due August 1, 2020. The Bonds were issued pursuant to ComEd’s Mortgage dated July 1, 1923, as amended and supplemented by supplemental indentures, including the Supplemental Indenture dated August 1, 1944 (Mortgage) and the Supplemental Indenture dated as of July 12, 2010 (Supplemental Indenture). The Mortgage is a first mortgage on ComEd’s utility plant. The proceeds of the Bonds will be used by ComEd to refinance maturing first mortgage bonds, to make a contribution to an Exelon-sponsored pension plan in which ComEd participates and to fund other general corporate purposes. The Bonds were registered under the Securities Act of 1933, as amended, pursuant to ComEd’s Registration Statement on Form S-3 (Registration No. 333-158920), which was declared effective upon filing with the Securities and Exchange Commission on April 30, 2009.

The Bonds carry an interest rate of 4.00% per annum, which is payable semi-annually on February 1 and August 1, commencing February 1, 2011. The Bonds are redeemable at ComEd’s option (i) at any time prior to May 1, 2020 at a “make-whole” redemption price calculated as provided in the Supplemental Indenture, plus accrued and unpaid interest up to but excluding the redemption date, and (ii) on or after May 1, 2020, at a redemption price equal to 100% of the principal amount to be redeemed, plus accrued and unpaid interest up to but excluding the redemption date. A copy of the Supplemental Indenture, which sets forth the terms of the Bonds, is attached hereto as Exhibit 4.1 and is incorporated herein by reference.

In connection with the issuance of the Bonds, Sidley Austin LLP provided ComEd with the legal opinion attached to this Current Report as Exhibit 5.1.

A copy of the Underwriting Agreement dated July 26, 2010 between ComEd and Banc of America Securities LLC, Deutsche Bank Securities Inc., Loop Capital Markets LLC, Scotia Capital (USA) Inc. and U.S. Bancorp Investments, Inc., as representatives of the several underwriters named therein, is filed as Exhibit 1.1. to this Current Report. Banc of America Securities LLC, Deutsche Bank Securities Inc., Scotia Capital (USA) Inc. and U.S. Bancorp Investments, Inc. have banking affiliates who are lending parties in ComEd’s revolving facility. Some of the underwriters and their affiliates have engaged in, and may in the future engage in, investment banking and other commercial dealings in the ordinary course of business with ComEd and its affiliates. They have received customary fees and commissions for these transactions.

Section 9 – Financial Statements and Exhibits

(d) Exhibits.

The following exhibits are filed herewith and are exhibits to the Registration Statement on Form S-3, Registration No. 333-158920, as noted below:

* * * * *

This Current Report includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that are subject to risks and uncertainties. The factors that could cause actual results to differ materially from these forward-looking statements include those discussed herein as well as those discussed in (1) ComEd’s 2009 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) ComEd’s Second Quarter 2010 Quarterly Report on Form 10-Q 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 12; and (3) other factors discussed in filings with the Securities and Exchange Commission by ComEd. Readers are cautioned not to place undue reliance on these forward-looking statements, which apply only as of the date of this Current Report. ComEd does not undertake any obligation to publicly release any revision to its forward-looking statements to reflect events or circumstances after the date of this Current Report.

SIGNATURES

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

August 2, 2010

EXHIBIT INDEX