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                                                                    Exhibit 99.3
                                                            EXECUTION COPY
                      ASSUMPTION AND AMENDMENT AGREEMENT
            ASSUMPTION AND AMENDMENT AGREEMENT, dated as of April 15, 1998, made
by ▇▇▇▇ ENTERPRISES, INC., a California corporation, and ATLANTIC PROSPECT,
INC., a New York corporation (collectively, the "Additional Grantors"), in favor
of CANADIAN IMPERIAL BANK OF COMMERCE, as US Administrative Agent and Canadian
Administrative Agent (in such capacities, the "Administrative Agent") for the
banks and other financial institutions (the "Lenders") parties to the Credit
Agreement referred to below. All capitalized terms not defined herein shall have
the meaning ascribed to them in such Credit Agreement.
                              W I T N E S S E T H:
            WHEREAS, Outdoor Systems, Inc., a Delaware corporation (the
"Company"), and Mediacom Inc., a Canadian corporation (collectively, the
"Borrowers"), the Lenders and the Administrative Agent have entered into the
Fifth Amended and Restated Credit Agreement, dated as of August 15, 1997 (as
amended, supplemented or otherwise modified from time to time, the "Credit
Agreement");
            WHEREAS, in connection with the Credit Agreement, the Company and
certain of its Affiliates (other than the Additional Grantors) have entered into
the US Guarantee and Collateral Agreement, dated as of August 22, 1996 (as
amended, supplemented or otherwise modified from time to time, the "US Guarantee
and Collateral Agreement"), in favor of the US Administrative Agent for the
benefit of the Lenders;
            WHEREAS, the Credit Agreement requires the Additional Grantors to
become parties to the US Guarantee and Collateral Agreement; and
            WHEREAS, the Additional Grantors have agreed to execute and deliver
this Assumption and Amendment Agreement to become parties to the US Guarantee
and Collateral Agreement, and the Company has agreed to execute and deliver this
Assumption and Amendment Agreement to cause the Capital Stock of the Additional
Grantors that is owned by the Company to become Pledged Stock under the US
Guarantee and Collateral Agreement;
            NOW, THEREFORE, IT IS AGREED:
            1. Joinder. By executing and delivering this Assumption and
Amendment Agreement, the Additional Grantors, as provided in Section 8.16 of the
US Guarantee and Collateral Agreement, hereby become parties to the US Guarantee
and Collateral Agreement as Grantors thereunder with the same force and effect
as if originally named therein as Grantors and, without limiting the generality
of the foregoing, hereby expressly assume all obligations and liabilities of
Grantors thereunder. The information set forth in Annex A hereto is hereby added
to the information set forth in Schedules 1 through 6 to the US Guarantee and
Collateral Agreement. The Additional Grantors hereby represent and warrant that
each of the representations and warranties contained in Section 4 of the US
Guarantee and Collateral Agreement is true and correct on and as of the date
hereof (after giving effect to this Assumption and Amendment Agreement) as if
made on and as of such date.
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            2. Additional Pledged Agreement. By executing and delivering this
Assumption and Amendment Agreement, the Company hereby agrees that Schedule 2 of
the US Guarantee and Collateral Agreement is hereby amended by adding thereto
the information with respect to the shares of Capital Stock of the Additional
Grantors listed on Annex B hereto and that the lien created by the US Guarantee
and Collateral Agreement shall hereby be extended to cover such shares. The
Company hereby represents and warrants that each of the representations and
warranties contained in Section 4 of the US Guarantee and Collateral Agreement
is true and correct on and as of the date hereof (after giving effect to this
Assumption and Amendment Agreement) as if made on and as of such date. The
Company is delivering to the US Administrative Agent together with this
Assumption and Amendment Agreement the certificates representing the shares of
Capital Stock of the Additional Grantors listed on Annex B hereto, together
with, in the case of each such certificate, a duly executed blank stock power.
            3. GOVERNING LAW. THIS ASSUMPTION AND AMENDMENT AGREEMENT SHALL BE
GOVERNED BY, AND CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE LAW OF THE
STATE OF NEW YORK.
            IN WITNESS WHEREOF, the undersigned have caused this Assumption and
Amendment Agreement to be duly executed and delivered as of the date first above
written.
                                        ▇▇▇▇ ENTERPRISES, INC.
                                        By: /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇
                                            -----------------------
                                            Name: ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇
                                            Title: Chairman
                                      
                                        ATLANTIC PROSPECT, INC.
                                        By: /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇
                                            -----------------------
                                            Name: ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇
                                            Title: Chairman
                                      
                                        OUTDOOR SYSTEMS, INC.
                                        By: /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇
                                            -----------------------
                                            Name: ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇
                                            Title: Chairman
                                     
Agreed to:
CANADIAN IMPERIAL BANK OF COMMERCE,
as US Administrative Agent
By: /s/
    -------------------------------
Name:
Title:
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                                   ANNEX A
SCHEDULE 1 NOTICE ADDRESSES OF GUARANTORS
           1.  ▇▇▇▇ Enterprises, Inc.
               ▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇
               ▇▇▇▇▇▇▇, ▇▇▇▇▇▇▇ ▇▇▇▇▇
               Attention:  ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇
           2.  Atlantic Prospect, Inc.
               ▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇
               ▇▇▇▇▇▇▇, ▇▇▇▇▇▇▇ ▇▇▇▇▇
               Attention:  ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇
SCHEDULE 2 DESCRIPTION OF PLEDGED SECURITIES
           PLEDGED STOCK:
               ISSUER               CLASS OF STOCK    STOCK CERT.#   # OF SHARES
                                                            
           ▇▇▇▇ Enterprises, Inc.      Common              7           2,500.0
           Atlantic Prospect, Inc.     Common              1             100.0
                                   
           PLEDGED NOTES:
               None
SCHEDULE 3 FILINGS AND OTHER ACTIONS REQUIRED TO PERFECT SECURITY INTERESTS
           UNIFORM COMMERCIAL CODE FILINGS
               ENTITY                            JURISDICTION
           ▇▇▇▇ Enterprises, Inc.                Arizona    - Secretary of State
                                                 California - Secretary of State
           Atlantic Prospect, Inc.               Arizona    - Secretary of ▇▇▇▇▇
                                                 ▇▇▇ ▇▇▇▇   - ▇▇▇▇▇▇▇▇▇ ▇▇ ▇▇▇▇▇
                                                              ▇▇▇▇▇ ▇▇▇▇▇▇
           PATENT AND TRADEMARK FILINGS
                 None
           UNITED STATES
                 REGISTERED MARKS
                     None
                 PENDING APPLICATIONS
                     None
                 COMMON LAW MARKS
                     None
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           CANADA
                 COMMON LAW MARKS
                     None
           FILINGS REQUIRED TO PERFECT SECURITY INTEREST IN PATENT AND
           TRADEMARK FILINGS
                  None
           ACTIONS WITH RESPECT TO PLEDGED STOCK
                  None
           OTHER ACTIONS
                  None
SCHEDULE 4 LOCATION OF JURISDICTION OF ORGANIZATION AND CHIEF EXECUTIVE OFFICE
                  GRANTOR                                JURISDICTION
                                                         
           1.  ▇▇▇▇ Enterprises, Inc.                     California
               ▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇           
               ▇▇▇▇▇▇▇, ▇▇▇▇▇▇▇ ▇▇▇▇▇                    
               Attention:  ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇             
                                                         
           2.  Atlantic Prospect, Inc.                    New York
               ▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇    
               ▇▇▇▇▇▇▇, ▇▇▇▇▇▇▇ ▇▇▇▇▇
               Attention:  ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇
SCHEDULE 5 LOCATION OF INVENTORY AND EQUIPMENT
                       GRANTOR                                LOCATION
           1.  ▇▇▇▇ Enterprises, Inc.                    ▇▇▇▇ ▇▇▇▇▇▇▇ ▇▇▇▇▇▇
               ▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇           ▇▇▇ ▇▇▇▇▇▇▇, ▇▇ ▇▇▇▇▇
               ▇▇▇▇▇▇▇, ▇▇▇▇▇▇▇ ▇▇▇▇▇
           2.  Atlantic Prospect, Inc.                        None(1)
               ▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇ ▇▇▇▇▇▇ ▇▇▇▇▇▇▇
               ▇▇▇▇▇▇▇, ▇▇▇▇▇▇▇ ▇▇▇▇▇
SCHEDULE 6 COPYRIGHTS AND COPYRIGHT LICENSES, PATENT AND PATENT LICENSES,
           TRADEMARKS AND TRADEMARK LICENSES
               None
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(1) This company was incorporated for the purpose of holding, and holds a 100%
interest in, the mortgage on property located at ▇▇▇-▇▇▇ ▇▇▇▇▇▇▇▇ ▇▇▇▇▇▇,
▇▇▇▇▇▇▇▇, ▇▇▇▇▇ ▇▇▇▇▇▇, ▇▇▇ ▇▇▇▇ ▇▇▇▇▇.
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ANNEX B
DESCRIPTION OF PLEDGED SECURITIES
PLEDGED STOCK
Issuer                   Class of Stock  Stock Certificate Number  # of Shares
------                   --------------  ------------------------  -----------
                                                          
▇▇▇▇ Enterprises, Inc.      Common                  7                  2,500
Atlantic Prospect, Inc.     Common                  1                    100