(As filed December 20, 2001)
                                                                File No. 70-9645

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                     POS-AMC
                        (Post-Effective Amendment No. 4)
                                       to
                                    FORM U-L
                             APPLICATION/DECLARATION
                                      UNDER
                 THE PUBLIC UTILITY HOLDING COMPANY ACT OF 1935

                               EXELON CORPORATION
                           COMMONWEALTH EDISON COMPANY
                            10 South Dearborn Street
                                   37th Floor
                             Chicago, Illinois 60603

                               PECO ENERGY COMPANY
                               2301 Market Street
                        Philadelphia, Pennsylvania 19101

                         EXELON GENERATION COMPANY, LLC
                                 300 Exelon Way
                       Kenneth Square, Pennsylvania 19348

                      EXELON INFRASTRUCTURE SERVICES, INC.
                                 200 Yale Avenue
                           Morton, Pennsylvania 19070

                              EXELON SERVICES INC.
                              2315 Enterprise Drive
                           Westchester, Illinois 60154

             (Names of companies filing this statement and addresses
                        of principal executive offices)
            --------------------------------------------------------

                               EXELON CORPORATION

          (Name of top registered holding company parent of applicants)
             -------------------------------------------------------

John W. Rowe Corbin A. McNeill, Jr. Co-Chief Executive Officer Co-Chief Executive Officer Exelon Corporation Exelon Corporation 10 South Dearborn Street 2301 Market Street 37th Floor P.O. Box 8699 Chicago, Illinois 60603 Philadelphia, Pennsylvania 19101 (Names and addresses of agents for service) ------------------------------------------------------ The Commission is requested to send copies of all notices, orders and communications in connection with this Application/Declaration to: Harvey B. Dikter, Senior Vice President and General Counsel Exelon Infrastructure Services, Inc. 200 Yale Avenue Morton, Pennsylvania 19070 William T. Baker, Jr. Esq. Thelen Reid & Priest LLP 40 West 57th Street New York, New York 10019

Post-Effective Amendment No. 1, filed in this proceeding on April 4, 2001, as amended by Post-Effective Amendment No. 3,(1) filed on December 14, 2001, is hereby further amended as follows: The reference to "EES" in the new paragraph added by Post-Effective Amendment No. 1 at the end of Item 1.3 is hereby changed to "ES". SIGNATURES Pursuant to the requirements of the Public Utility Holding Company Act of 1935, the undersigned companies have duly caused this statement to be signed on their behalves by the undersigned thereunto duly authorized. EXELON CORPORATION By: /s/ Randall Mehrberg --------------------- Name: Randall Mehrberg Title: Senior Vice President and General Counsel EXELON INFRASTRUCTURE SERVICES, INC. By: /s/ Harvey B. Dikter -------------------- Name: Harvey B. Dikter Title: Senior Vice President and General Counsel EXELON SERVICES INC. By: /s/ Kenneth H. Beard -------------------- Name: Kenneth H. Beard Title: President (signatures continued on next page) - -------- (1) Post-Effective Amendment No. 2, which was filed on October 1, 2001, relates to matters that are not the subject of Post-Effective Amendment No. 1.

COMMONWEALTH EDISON COMPANY PECO ENERGY COMPANY EXELON GENERATION COMPANY,LLC BY EXELON CORPORATION By: /s/ Randall Mehrberg --------------------- Name: Randall Mehrberg Title: Senior Vice President and General Counsel Date: December 20, 2001