EXHIBIT 4.2 AMENDMENT NUMBER FOUR TO STOCKHOLDERS AGREEMENT AMENDMENT, dated effective October 1, 1999, to the Stockholders Agreement (the "Stockholders Agreement") dated as of August 21, 1998, among CROWN CASTLE INTERNATIONAL CORP., a Delaware corporation (the "Company") and each of the STOCKHOLDERS of the Company listed on Schedule I thereto (collectively, the "Stockholders" and each individually, a "Stockholder"); WHEREAS, the Company and the Stockholders desire to amend the Stockholders Agreement to provide that Shares distributed by a Stockholder to a partner, member, stockholder or beneficiary of such Stockholder shall cease to be a subject to the Stockholders Agreement and the distribution of such Shares shall not cause the distributee to be a Stockholder; WHEREAS, pursuant to Section 6.04 of the Stockholders Agreement, the Stockholders Agreement may be amended by the mutual agreement of the parties thereto; and WHEREAS, the Company and the Stockholders have agreed to amend the Stockholders Agreement in the manner hereinafter set forth. NOW, THEREFORE, in consideration of the promises and the respective agreements, acknowledgments and confirmations hereinafter set forth and set forth in the Stockholders Agreement, the parties hereto agree as follows: SECTION 1. Amendment. (a) Section 2.05 of the Agreement is amended and restated to read as follows: "SECTION 2.05. Certain Transferees to Execute Agreement. Each Stockholder agrees that it will not, directly or indirectly, sell or otherwise transfer any Shares held by such Stockholder to any of its Affiliates or permitted transferees, unless, prior to the consummation of any such sale or transfer, the Affiliate or permitted transferee to whom such sale or transfer is proposed to be made (a "Prospective Transferee") (i) executes and delivers to the Company and each other party to this Agreement a counterpart hereof and (ii) represents and warrants in writing to the Company that such counterpart has been duly authorized, executed and delivered by such Prospective Transferee and is a legal, valid and binding obligation of such Prospective Transferee enforceable against it in accordance with its terms, subject to insolvency, bankruptcy and other laws affecting creditors generally. Upon the execution and delivery by such Prospective Transferee of the documents referred to in the preceding sentence, such Prospective Transferee shall be deemed a "Stockholder" for the purposes of this Agreement, and shall have the rights and be subject to the obligations of a Stockholder hereunder with respect to the Shares held by such Prospective Transferee. The provisions of this Section 2.05 shall not apply to any distribution of Shares by a Stockholder to its partners (in the case of a partnership), members (in the case of a limited liability company), stockholders (in the case of a corporation) or beneficiaries (in the case of a trust) of such Stockholder whether or not the distributee is a Stockholder, Affiliate or permitted transferee." (b) Section 2.06 of the Agreement is amended and restated to read as follows: "SECTION 2.06. Sale to a Third Party; Distributions. If a sale or transfer of Shares is made by a Stockholder to a third party (except for transfers within the TDF Group, the Berkshire Group, the Centennial Group, the Candover Group, the Nassau Group or otherwise to an Affiliate or to any permitted transferee) (a "Third Party Transferee"), such Shares shall immediately cease to be subject to this Agreement and such Third Party Transferee will not become a Stockholder for purposes of this Agreement. If a sale or transfer of Shares results in the selling Stockholder or a permitted transferee ceasing to own any Shares, such selling Stockholder shall cease to be a Stockholder for purposes of this Agreement. If a Stockholder distributes Shares to any of its partners (in the case of a partnership), members (in the case of a limited liability company), stockholders (in the case of a corporation) or beneficiaries (in the case of a trust), such Shares shall immediately cease to be subject to this Agreement (whether or not the distributee is a Stockholder, a member of the TDF Group, the Berkshire Group, the Centennial Group, the Candover Group, the Nassau Group, an Affiliate or a permitted transferee) and such partner, member, stockholder or beneficiary will not become a Stockholder for purposes of this Agreement as a result of such distribution." SECTION 3. Construction: Continuing Effect. This Agreement shall be construed in connection with and as part of the Stockholders Agreement and each reference to the Stockholders Agreement contained in any other document shall mean the Stockholders Agreement as amended hereby. As amended hereby, the Stockholders Agreement shall continue in full force and effect. Terms used but not defined in this Amendment Number Four to Stockholders Agreement shall have the meaning ascribed to such term in the Stockholders Agreement. SECTION 4. Counterparts. This Agreement may be executed in one or more counterparts, each of which shall be deemed an original but which together shall constitute but one instrument. It shall not be necessary for each party to sign each counterpart so long as every party has signed at least one counterpart. IN WITNESS WHEREOF, each party hereto has executed this Agreement effective as of the day and year first above written. CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 CROWN CASTLE INTERNATIONAL CORP. By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 TELEDIFFUSION DE FRANCE INTERNATIONAL S.A. By: ____________________________________ Name: Title: August ____, 1999 DIGITAL FUTURE INVESTMENTS B.V. By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 CANDOVER INVESTMENTS, PLC By: ____________________________________ Name: Title: August ____, 1999 CANDOVER (TRUSTEES) LIMITED By: ____________________________________ Name: Title: August ____, 1999 CANDOVER PARTNERS LIMITED (as general partner of the Candover 1994 UK Limited Partnership) By: ____________________________________ Name: Title: August ____, 1999 CANDOVER PARTNERS LIMITED (as general partner of the Candover 1994 UK No. 2 Limited Partnership) By: ____________________________________ Name: Title: August ____, 1999 CANDOVER PARTNERS LIMITED (as general partner of the Candover 1994 US No. 1 Limited Partnership) By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 CANDOVER PARTNERS LIMITED (as general partner of the Candover 1994 US No. 2 Limited Partnership) By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 _________________________________________ TED B. MILLER, JR. August ____, 1999 _________________________________________ ROBERT H. SINGLETON, Trustee The Miller 1996 Gift Trusts CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August____, 1999 ____________________________________ ROBERT A. CROWN August ____, 1999 ____________________________________ BARBARA A. CROWN August ____, 1999 RC INVESTORS CORP. a Delaware corporation By: ________________________________ Name: ______________________________ Title: _______________________________ August ____, 1999 BC INVESTORS CORP. a Delaware corporation By: ________________________________ Name: ______________________________ Title: _______________________________ August ____, 1999 RACG Holdings LLC Limited Liability Company By: ________________________________ Name: ______________________________ Title: _______________________________ August ____, 1999 BACG Holdings LLC Limited Liability Company By: ________________________________ Name: ______________________________ Title: _______________________________ CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 BERKSHIRE FUND III, A LIMITED PARTNERSHIP By: ____________________________________ a Managing Member August ____, 1999 BERKSHIRE FUND IV, LIMITED PARTNERSHIP By: ____________________________________ a Managing Member August ____, 1999 BERKSHIRE INVESTORS LLC By: ____________________________________ a Managing Member CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 NASSAU CAPITAL PARTNERS II, L.P. By Nassau Capital L.L.C., its General Partner By: ____________________________________ Name: Title: August ____, 1999 NAS PARTNERS I, L.L.C. By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 FAY, RICHWHITE COMMUNICATIONS LIMITED By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 PNC VENTURE CORP. By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 NEW YORK LIFE INSURANCE COMPANY By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 HARVARD PRIVATE CAPITAL HOLDINGS, INC. By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 AMERICAN HOME ASSURANCE COMPANY By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 THE NORTHWESTERN MUTUAL LIFE INSURANCE COMPANY By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 CENTENNIAL FUND IV, L.P. By: Centennial Holdings V, L.P. its general partner By: ____________________________________ Name: Title: August ____, 1999 CENTENNIAL FUND V, L.P. By: Centennial Holdings V, L.P. its general partner By: ____________________________________ Name: Title: August ____, 1999 CENTENNIAL ENTREPRENEURS FUND V, L.P. By: Centennial Holdings V, L.P. its general partner By: ____________________________________ Name: Title: CROWN CASTLE INTERNATIONAL CORP. Amendment Number Four to Stockholders Agreement August ____, 1999 PRIME VIII, L.P. By: Prime SKA I, LLC its general partner By: ____________________________________ Name: Title: