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                                                      Registration No. 333-50415


                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D. C. 20549

                         ------------------------------
                         Post Effective Amendment No. 1
                                       TO
                                    FORM S-4

                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

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

                          THE COLONIAL BANCGROUP, INC.

             (Exact name of Registrant as specified in its charter)

       Delaware                       6711                     63-0661573
(State of Incorporation)   (Primary Standard Industrial     (I.R.S. Employer
                            Classification Code Number)    Identification No.)

     One Commerce Street, Suite 800                         (334) 240-5000
       Montgomery, Alabama 36104                            (Telephone No.)
(Address of principal executive offices)

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                               William A. McCrary
                                    Secretary
                              Post Office Box 1108
                            Montgomery, Alabama 36101
                     (Name and address of agent for service)

                                   Copies to:

                                Willard H. Henson
                         Miller, Hamilton, Snider & Odom
                         One Commerce Street, Suite 305
                            Montgomery, Alabama 36104

            Approximate date of commencement of proposed sale to the
           public: As soon as practicable after the effective date of
                          this Registration Statement.

         If the securities being registered on this Form are being offered in
connection with the formation of a holding company and there is compliance with
General Instruction G, check the following box. [ ]


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         The Colonial BancGroup, Inc. ("BancGroup") registered 1,263,235 shares
of its Common Stock on Form S-4, registration no. 333-50415, in connection with
the acquisition of Commercial Bank of Nevada ("Commercial"), a Nevada state
bank. Such registration was declared effective on April 29, 1998.

         A total of 842,157 shares were issued in the merger on June 15, 1998.
Subsequent to the merger, BancGroup issued a 2 for 1 stock split, effected in
the form of a 100% stock dividend (the "Stock Split"). Pursuant to SEC Rule
416(b), the registration statement is deemed to cover the additional shares
resulting from the Stock Split. Accordingly, the Form S-4, registration no.
333-50415, is deemed to register a total of 2,526,470 shares of BancGroup common
stock. Giving effect to the Stock Split, a total of 1,684,314 shares would be
deemed to have been issued in the merger. Pursuant to the undertaking given by
BancGroup in such registration statement in accordance with Regulation S-K, item
512(a)(3), BancGroup hereby removes 842,156 shares from registration, which
represents the number of shares registered less the number of shares issued in
the merger.

                                    SIGNATURE

         Pursuant to Regulation S-K, item 512(a)(3) and SEC Rule 478(a)(4), the
undersigned registrant hereby executes this post effective amendment to its
registration statement on Form S-4 to remove from registration certain shares
not issued and has caused this registration statement to be signed on its behalf
by the undersigned, thereunto duly authorized, in the City of Montgomery,
Alabama, on the 2nd day of February, 2001.

                                    THE COLONIAL BANCGROUP, INC.

                                    By: /s/ W. Flake Oakley, IV
                                       ----------------------------------------
                                       W. Flake Oakley, IV
                                       Chief Financial Officer and
                                       duly authorized agent for
                                       service