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                                                                    EXHIBIT 4.28

                             SUPPLEMENTAL INDENTURE
                       TO INDENTURE DATED AUGUST 15, 1997



         THIS SUPPLEMENTAL INDENTURE dated as of December 23, 1999, is delivered
pursuant to Section 4.11 of the Indenture dated as of August 15, 1997 (as
heretofore or hereafter modified and supplemented and in effect from time to
time, the "1997 Indenture") among OUTDOOR COMMUNICATIONS, INC., a Delaware
corporation, certain of its subsidiaries (the "Guarantors") and FIRST UNION
NATIONAL BANK, a national banking corporation, as Trustee (the "Trustee") (all
terms used herein without definition having the meanings ascribed to them in the
1997 Indenture).

         The undersigned hereby agree that:

         1. The undersigned is a Guarantor under the 1997 Indenture with all of
the rights and obligations of the Guarantors thereunder.

         2. The undersigned have granted, ratified and confirmed, in the form
and substance of Exhibit B to the 1997 Indenture, the Guarantee provided for by
Article XI of the 1997 Indenture.

         3. The undersigned hereby represents and warrants that the
representations and warranties set forth in the 1997 Indenture, to the extent
relating to the undersigned as Guarantor, are correct on and as of the date
hereof.

         4. All notices, requests and other communications provided for in the
1997 Indenture should be delivered to the undersigned at the following address:

                  Keith A. Istre
                  Vice President - Finance and
                  Chief Financial Officer
                  Lamar Media Corp. and its Subsidiaries
                  5551 Corporate Blvd.
                  Baton Rouge, LA 70808

         5. A counterpart of this Supplemental Indenture may be attached to any
counterpart of the 1997 Indenture.

         6. This Supplemental Indenture shall be governed by and construed in
accordance with the internal laws of the State of New York.


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         IN WITNESS WHEREOF, the undersigned have caused this Supplemental
Indenture to be duly executed as of the day and year first above written.

                                        Guarantor:

                                        LAMAR FLORIDA, INC.

                                        a Florida corporation

                                        By:  /s/ Keith A. Istre
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                                           Keith A. Istre
                                           Vice President - Finance and
                                           Chief Financial Office
Attest:


By:  /s/ James R. McIlwain
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   James R. McIlwain, Secretary

Accepted:

FIRST UNION NATIONAL BANK, as Trustee

By: /s/ JAMES LONG
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Title: Corperate Trust Officer
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