Document:

<PAGE>

                                                                   Exhibit 10.28
                                                                   -------------

                         STOCKHOLDER/OPTIONEE AGREEMENT

         AGREEMENT made and entered into, as of October 11, 2001, by and among
ATC Mexico Holding Corp., a Delaware corporation ("Holding"), American Tower
Corporation, a Delaware corporation ("ATC"), American Tower International, Inc.,
a Delaware corporation ("ATC International"), J. Michael Gearon, Jr., an
individual residing in Atlanta, Georgia ("Gearon") and the Persons who from time
to time execute a counterpart of this Agreement (individually a "Stockholder"
and collectively the "Stockholders" which terms shall include Gearon in his
capacity as such).

                              W I T N E S S E T H:
                              --------------------

         WHEREAS, ATC and Gearon desire to provide for the organization, funding
and management of Holding;

         WHEREAS, the Stockholders other than Gearon will be acquiring from
Holding, and Holding will issue to such Stockholders, pursuant to a 2001 Stock
Option Plan (the "Plan") to be adopted pursuant to the provisions of Section 8,
an option (individually an "Option" and collectively the "Options") to acquire
shares of Holding Common Stock; and

         WHEREAS, Holding is unwilling to grant the Options, or to permit their
exercise, without the assurances with respect to its ability to acquire the
Option and/or Common Stock on the terms and conditions of this Agreement and
with respect to investment intent provided herein; and

         WHEREAS, the Stockholders are unwilling to accept or exercise, as the
case may be, the Option without assurances of the ability to dispose of the
Holding Securities on the terms and conditions of this Agreement;

         WHEREAS, it is in the best interests of Holding and of all of the
owners of shares of Holding Common Stock to ensure the business success of
Holding through the preservation and encouragement of harmonious relationships
within Holding; and

         WHEREAS, the parties agree that these goals will be furthered by
providing for certain restrictions as to the transferability of the shares of
Holding Common Stock owned by the holders thereof and by providing for
succession of ownership thereof;

         NOW, THEREFORE, in consideration of the premises, of the mutual
covenants hereinafter set forth, as a condition to the grant and/or exercise of
the Options, and other valuable consideration, the receipt, adequacy and
sufficiency whereof are hereby acknowledged, the parties hereto, intending to be
legally bound, do hereby covenant and agree as follows:

         Section 1. Definitions. As used herein, unless the context otherwise
                    -----------
requires, the terms used herein which are not defined herein and are defined in
Appendix A shall have the respective meanings set forth in Appendix A. Terms
defined in the singular shall have a comparable meaning when used in the plural,
and vice versa, and the reference to any gender shall be deemed to include all
genders. Unless otherwise defined or the context otherwise clearly requires,
terms for which meanings are provided in this Agreement shall have such meanings
when used in each document or other instrument executed or required to be
executed pursuant hereto or thereto or otherwise delivered, from time to time,
pursuant hereto or thereto. References to "hereof," "herein" or similar terms
are intended to refer to this

<PAGE>

Agreement as a whole and not a particular section, and references to "this
Section" are intended to refer to the entire section and not a particular
subsection thereof.

         Section 2. Representations and Warranties of Parties. Each of the
                    -----------------------------------------
parties represents and warrants as follows:

                  (a) Authority to Execute and Perform Agreements. Such party
                      -------------------------------------------
         (if an Entity) has been duly organized and is validly existing as an
         Entity in good standing in its jurisdiction of organization as
         indicated in the preamble of this Agreement and has all requisite power
         and authority (corporate, partnership, limited liability company, and
         other) and has in full force and effect all governmental authorizations
         and private authorizations necessary to enable it to execute and
         deliver, and to perform its obligations under, this Agreement. The
         execution and delivery of this Agreement by such party (if an Entity)
         have been duly authorized by all requisite corporate, partnership,
         limited liability company, or other organizational action, if any, on
         the part of such party. This Agreement has been duly executed and
         delivered and constitutes the legal, valid and binding obligation of
         such party enforceable against such party in accordance with its terms,
         except as (i) the enforceability thereof may be limited by bankruptcy,
         insolvency or similar laws affecting the enforcement of creditors'
         rights generally and (ii) the availability of equitable remedies may be
         limited by equitable principles of general applicability.

                  (c) No Conflict; Required Filings and Consents. Neither the
                      ------------------------------------------
         execution and delivery by such party of this Agreement, nor the
         consummation of the transactions contemplated by this Agreement, nor
         compliance with the terms, conditions and provisions hereof by such
         party:

                           (i) will conflict with, or result in a breach or
                  violation of, or constitute a default under, any applicable
                  Law, or will conflict with, or result in a breach or violation
                  of, or constitute a default under, or permit the acceleration
                  of any obligation or liability in, or but for any requirement
                  of the giving of notice or passage of time or both would
                  constitute such a conflict with, breach or violation of, or
                  default under, or permit any acceleration in, any organization
                  document (in the case of an Entity), governmental
                  authorization or material agreement of such party;

                           (ii) will result in or permit the creation or
                  imposition of any Lien upon any property or asset of such
                  party; or

                           (iii) will require any approval or action of, or
                  filing with, any governmental authority.

         Section 3. Funding Covenants of ATC and Gearon. ATC and Gearoncovenant
                    -----------------------------------
and agree as follows:

                  (a) ATC Additional Common Stock Investments. If ATC and/or its
                      ---------------------------------------
         Affiliates have not, on or prior to the date hereof, invested an
         aggregate of US$88,000,000 in Holding, ATC will, at such time and from
         time to time as required to finance the business and operations of
         Holding, cause ATC International (or another Affiliate of ATC) to
         purchase additional shares of Holding Common Stock; provided, however,
         that in no event shall ATC and its Affiliates be required or, without
         the written consent of Gearon, permitted to invest more than an
         aggregate of US$88,000,000 in Holding Common Stock. Payment for all
         such shares shall be in the form of wire transfer of immediately
         available funds.

                                       -2-

<PAGE>

          (b) Additional Gearon Investments. If Gearon has not, on or prior to
              -----------------------------
          the date hereof, invested an aggregate of US$8,400,000 in Holding, he
          will, simultaneously with ATC making additional purchases of Holding
          Common Stock, purchase additional shares of Holding Common Stock such
          that Gearon shall on each such occasion purchase, at the same price
          per share as ATC, eighty-four nine hundred sixty-fourth (84/964th) of
          the number of shares being purchased by ATC; provided, however, that
          in no event shall Gearon be required to invest more than an aggregate
          of US$8,400,000 in Holding Common Stock or to make any other
          investment in Holding. Payment for all such shares shall be in the
          form of wire transfer of immediately available funds to the extent of
          twenty percent (20%) of each purchase and the balance in the form of a
          promissory note in the form attached hereto and made a part hereof as
          Exhibit A (the "Gearon Note"); provided, however, that Gearon shall
          (i) have the right, at his sole discretion, to make payment for all
          such shares in the form of wire transfer of immediately available
          funds, and (ii) not, except as hereinafter provided, be obligated to
          invest more than US$1,680,000 in the form of cash. Anything in this
          Section or elsewhere in this Agreement to the contrary
          notwithstanding, Gearon shall be required to make payment in full in
          the form of wire transfer of immediately available funds for all
          shares of Holding Common Stock proposed to be sold or otherwise
          Transferred (other than any pledge by it to Holding pursuant to the
          Pledge Agreement) by him pursuant to any provision of this Agreement
          prior to any such sale or Transfer.

                  (c) ATC Other Investments. ATC shall have the right, but not
                      ---------------------
         the obligation, to provide, or to cause ATC International (or another
         Affiliate of ATC) to provide, additional funds as are required, from
         time to time, to finance the business and operations of Holding. If ATC
         elects, in its sole discretion, to provide (or cause to be provided)
         such funds, they shall be invested in either 10% subordinated notes
         (which shall be prepayable at any time by Holding and shall be
         nonrecourse to Gearon and the other Stockholders) or nonconvertible
         preferred stock (bearing dividends at 10% of its purchase price), at
         ATC's option. The other terms and conditions of the subordinated notes
         or preferred stock shall be commercially reasonable under the
         circumstances at the time of issuance. Payment for all such investments
         shall be in the form of wire transfer of immediately available funds.

                  (d) Third Party Investments/Equity Investments. ATC and Gearon
                      ------------------------------------------
         will consider, from time to time, the possibility of issuing and/or
         selling shares of Holding Common Stock or other forms of equity
         participation to individuals involved solely in the business,
         management and operation of Holding in Mexico (and not in the business,
         management or operations of any Affiliate of Holding other than those
         doing business solely in Mexico), it being the understanding of the
         parties that any such participation would dilute, on a pro rata basis,
         the interests of ATC and Gearon.

         Section 4. Designation of Directors; Voting Agreement; Corporate
                    -----------------------------------------------------
Governance. Each of the parties covenants and agrees with the other parties as
---------
follows:

                  (a) The Board of Directors of Holding (the "Holding Board")
         shall be composed at all times of three (3) persons. ATC International
         shall be entitled to designate for nomination for election, and have
         elected, to the Holding Board two persons who shall be the Chief
         Executive Officer and the Chief Financial Officer of ATC, unless the
         Board of Directors of ATC International shall otherwise determine.
         Gearon shall be entitled to designate for nomination for election, and
         have elected, to the Holding Board one person who shall be Gearon,
         unless Gearon shall otherwise determine with the prior approval of ATC,
         such approval not to be unreasonably withheld, delayed or conditioned.

                                       -3-

<PAGE>

                  (b) Holding shall provide ATC International and Gearon with at
         least twenty (20) days' prior notice in writing of any intended mailing
         of notice to stockholders for a meeting at which directors are to be
         elected. ATC and Gearon shall notify Holding in writing within ten (10)
         days of actual receipt of such notice of the person designated by him
         as nominee for election as a director. In the absence of any notice
         from ATC International or Gearon, as the case may be, the director or
         directors then serving and previously designated by him shall be deemed
         to have been redesignated.

                  (c) Any director designated by ATC International or Gearon
         shall be subject to removal for cause by the vote of (i) the directors
         of Holding to the extent permitted by applicable Law or (ii) the
         stockholders of Holding in accordance with applicable Law. ATC
         International and Gearon shall also be entitled to require that any
         member of the Holding Board so designated by it or him pursuant to this
         Section be removed or replaced by it or him.

                  (d) In the event any designee for nomination of ATC
         International or Gearon as director shall cease for any reason to serve
         as a director, including without limitation removal pursuant to the
         preceding paragraph or resignation, ATC International or Gearon, as the
         case may be, shall have the right to designate a replacement to fill
         such vacancy upon notice to Holding. Holding shall, unless Holding
         Board shall have elected such designee to Holding Board, solicit
         stockholder approval for the election of such nominee as a director in
         accordance with the provisions of this Section.

                  (e) ATC International and Gearon covenant and agree that so
         long as the other has the right to nominate a director to Holding Board
         in accordance with the provisions of this Agreement, at any meeting of
         the stockholders of Holding, however called, and at every adjournment
         thereof, and in any action by written consent of the stockholders of
         Holding, to vote all of the shares of capital stock of Holding entitled
         to vote thereon then owned or controlled by such Person in favor of the
         election of the nominee or nominees of the other pursuant to the
         provisions of this Section.

                  (f) ATC International covenants and agrees that, until the
         occurrence of a Forfeiture Event or the earlier termination by Gearon
         of his employment with Holding, whether with or without Good Reason, it
         will cause its nominees as directors to vote for the election of Gearon
         as president of Holding. It is also the understanding of the parties,
         that Gearon's compensation shall, taking into account the compensation
         to be paid to him by Other Holding, ATC and its subsidiaries, be
         determined annually by the Holding Board, all of which (other than
         US$100,000 (subject to proportionate increased based on future
         increases for other ATC senior management), which is to be paid by ATC)
         shall be paid by Holding or Other Holding.

         Section 5. Restrictions on Transfers of Holding Securities. Without the
                    -----------------------------------------------
written consent of ATC, except in accordance with the provisions of Section 6 or
pursuant to a Permitted Transfer, neither Gearon nor any other Stockholder shall
Transfer all or any part of the Holding Securities at the time held by it to any
Person (a) prior to July 1, 2006 and (b) thereafter except in accordance with
the provisions of Section 7.

         Section 6. Put and Call; Tagalong Right.
                    ----------------------------

         (a) Gearon Put. Gearon may, at any time after the soonest to occur of
             ----------
(i) July 1, 2004, (ii) an ATC Change of Control, (iii) a Holding Change of
Control, or (iv) his death or Disability, require ATC to purchase at the
Put/Call Price for the Holding Securities of all but not less than all of the
Holding

                                       -4-

<PAGE>

Securities then owned by him. Any such election (which may not, in any event, be
made prior to the date that is six (6) months and one (1) day after the date of
this Agreement) shall be made by written notice from Gearon to ATC (the "Put
Notice") of its election to that effect. Gearon shall send a copy of the Put
Notice to each of the other Stockholders. In such event, each of the other
Stockholders shall have the right, exercised by written notice to ATC delivered
within twenty (20) days of the mailing of the Put Notice to him, to require ATC
to purchase at the Put/Call Price for the Holding Securities to be sold by such
Stockholder (an "Electing Put Stockholder") all but not less than all of the
Holding Securities then owned by each Electing Put Stockholder. Gearon may give
the Put Notice at any time after December 31, 2003. For purposes of this Section
6(a), the Put/Call Price shall be determined as of the later of July 1, 2004 or
the date of the Put Notice; provided, however, with respect to each Electing Put
Stockholder who has not held the Holding Securities proposed to be sold by him
for a period of at least six (6) months and one (1) day as of the date of the
Put Notice, the Put/Call Price shall be determined as of the date such Holding
Securities were held by him for a period of at least six (6) months and one (1)
day.

         The closing pursuant to this Section shall occur at 10:00 a.m., local
time, on the later of July 1,2004 or the sixtieth (60th) day (or, if such day is
not a Business Day, the next succeeding Business Day) following the date of
receipt by ATC of the Put Notice, at the principal executive offices of ATC, or
such other time, date and place as ATC and Gearon shall reasonably agree (notice
of which shall be given by ATC to each Electing Put Stockholder); provided,
however, notwithstanding the foregoing, if, on the proposed closing date, any
Electing Stockholder has not held the Holding Securities proposed to be sold by
him for a period of at least six (6) months and one (1) day, then the closing
with respect to those Holding Securities shall occur at 10:00 a.m., local time,
on the tenth (10th) day (or, if such day is not a Business Day, the next
succeeding Business Day) following the expiration of such six (6) months and one
(1) day. Each of the following (unless and except to the extent waived by ATC
and Gearon) shall be a condition of the obligation of ATC, Gearon and each
Electing Put Stockholder to proceed with any such purchase and sale: (i) ATC and
Gearon shall have obtained all lender and other third-party consents, if any,
required in connection with such purchase and sale, (ii) there shall be no suit,
action or proceeding pending on the date of closing before or by any court or
other governmental authority seeking to restrain or prohibit, or material
damages or other relief in connection with, the purchase and sale, and (iii)
ATC, Gearon and the Electing Put Stockholders shall have entered into a
securities purchase agreement in form, scope and substance customary in
comparable transactions and reasonably satisfactory to ATC and Gearon, including
representations and warranties, covenants, closing certificates and opinions,
and indemnities.

         (b) ATC Call. ATC may, at any time after (i) July 1, 2005, require
             --------
Gearon to sell at the Put/Call Price and each other Stockholder to sell at the
Put/Call Price for the Holding Securities to be sold by him all but not less
than all of the Holding Securities then owned by him, or (ii) the soonest to
occur of (x) the death or Disability of Gearon, (y) a Gearon Termination Event,
or (z) a Forfeiture Event require each member of the Gearon Group to sell at the
Put/Call Price all but not less than all of the Holding Securities then owned by
him. Any such election (which may not, in any event, be made prior to the date
that is six (6) months and one (1) day after the date of this Agreement) shall
be made by written notice from ATC to Gearon and, as applicable, each other
Stockholder (the "Call Notice") of his election to that effect. ATC may give the
Call Notice at any time after December 31, 2004. For purposes of this Section
6(b), the Put/Call Price shall be determined as of the later of July 1, 2005 or
the date of the Call Notice; provided, however, with respect to each other
Stockholder who has not held the Holding Securities proposed to be sold by him
for a period of at least six (6) months and one (1) day as of the date of the
Call Notice, the Put/Call Price shall be determined as of the date such Holding
Securities were held by him for a period of at least six (6) months and one (1)
day. The closing pursuant to this Section shall occur at 10:00 a.m., local time,
on the later of July 1, 2005 or the sixtieth (60th) day (or, if such day is not
a Business Day, the next succeeding Business Day) following the date of receipt
by Gearon and, as

                                       -5-

<PAGE>

applicable, the other Stockholders of the Call Notice, at the principal
executive offices of ATC, or such other time, date and place as ATC and Gearon
shall reasonably agree (notice of which shall be given by ATC to each other
Stockholder); provided, however, notwithstanding the foregoing, if, on the
proposed closing date, any other Stockholder has not held the Holding Securities
proposed to be sold by him for a period of at least six (6) months and one (1)
day, then the closing with respect to those Holding Securities shall occur at
10:00 a.m., local time, on the tenth (10th) day (or, if such day is not a
Business Day, the next succeeding Business Day) following the expiration of such
six (6) months and one(1) day. Each of the following (unless and except to the
extent waived by ATC and Gearon) shall be a condition of the obligation of ATC,
Gearon and, as applicable, the other Stockholders to proceed with any such
purchase and sale: (i) ATC and Gearon shall have obtained all lender and other
third-party consents, if any, required in connection with such purchase and
sale, (ii) there shall be no suit, action or proceeding pending on the date of
closing before or by any court or other governmental authority seeking to
restrain or prohibit, or material damages or other relief in connection with,
the purchase and sale, and (iii) ATC, Gearon and, as applicable, the other
Stockholders shall have entered into a securities purchase agreement in form,
scope and substance customary in comparable transactions and reasonably
satisfactory to ATC and Gearon, including representations and warranties,
covenants, closing certificates and opinions, and indemnities.

         (c) Closing. At the closing Gearon and, as applicable, the Electing Put
             -------
Stockholders or the other Stockholders shall convey the Holding Securities to be
sold by it, properly endorsed for transfer, free of all Liens, and the
applicable Put/Call Price shall be paid by wire transfer of immediately
available funds or, at the election of ATC, shares of ATC Common Stock, or any
combination thereof. If the Gearon Note or any note from any Electing
Stockholder under Section 6(a) or any other Stockholder under Section 6(b) is
not paid in full at the closing in connection with the purchase of the Holding
Securities, ATC shall be entitled to apply the purchase price to the payment of
the unpaid principal amount thereof together with interest accrued and unpaid to
the closing. If any shares of ATC Common Stock are so delivered, they shall be
(i) valued at Fair Market Value as of the applicable closing date and (ii)
entitled to the benefit of the ATC Registration Rights Agreement. At the
election of ATC, the Holding Securities to be purchased may be acquired in the
name of one or more nominees, including without limitation Holding (whether or
not any such nominee is an Affiliate of ATC); provided, however, that any such
nominee is designated by written notice given at least five (5) days prior to
the date of closing.

         (d) Gearon and Other Stockholder Tagalong Right. In addition to the
             -------------------------------------------
rights of Gearon and the other Stockholders set forth in Section 6(a), if a
Holding Change of Control is likely to occur, ATC shall give prompt written
notice (the "Holding Change of Control Notice") of the likelihood of such
occurrence to Gearon and the other Stockholders, which notice shall describe, in
reasonable detail, the material terms and conditions of such transaction (the
"Holding Change of Control Transaction"). As a condition to the consummation of
any Transfer by ATC in connection with a Holding Change of Control Transaction,
Gearon and each other Stockholder shall have the right, exercised by written
notice to ATC within ten (10) business days of its receipt of the Holding Change
of Control Notice, to participate in the Holding Change of Control Transaction
on the same terms and conditions as ATC (i.e., to sell or otherwise transfer the
same relative proportion of its holdings as is ATC for the same type and per
share amount of consideration). If Gearon or any other Stockholder elects to
participate in a Holding Change of Control Transaction, it shall be required to
execute and deliver all of the documents executed and delivered by ATC and to be
bound by all of the same terms and conditions. Without limiting the generality
of the foregoing, if the Gearon Note or any note from any other Stockholder
electing to participate in a Holding Change of Control Transaction is not paid
in full at the closing in connection with a Holding Change of Control
Transaction, the purchaser shall be entitled to apply the purchase price to the
payment of the unpaid principal amount thereof together with interest accrued
and unpaid to the closing. The failure of Gearon or any other Stockholder to
give timely notice of its election to participate in a Holding Change of

                                       -6-

<PAGE>

Control Transaction in accordance with this Section 6(d) shall be deemed to be
an irrevocable election by it not to so participate.

         Section 7. Right of First Refusal on Holding Securities. If at any time
                    --------------------------------------------
on or after July 1, 2006 (prior to which time any such Transfer is prohibited
pursuant to the provisions of Section 5), Gearon or any other Stockholder (an
"Electing Offering Stockholder") desires to Transfer any Holding Securities to
any Third Party (the "Proposed Transfer"), it shall, prior to committing to the
Proposed Transfer to any such Third Party, offer to sell such Holding Securities
in accordance with the procedures, and upon the terms, set forth below.

                  (a) Gearon or the Electing Offering Stockholder shall send a
         written notice (a "Transfer Notice") to Gearon (in the case of an
         Electing Offering Stockholder), Holding and ATC, which Transfer Notice
         shall state that Gearon or the Electing Offering Stockholder intends to
         effect a Proposed Transfer and shall specify the number and class or
         type of Holding Securities (the "Offered Securities") subject to the
         Proposed Transfer, the name and address of the Third Party or Third
         Parties to whom such Transfer is proposed to be made (or if no
         particular Third Party is identified, then the general class of Persons
         to whom the Transfer is proposed to be made), a price per share which
         shall be the minimum price at which Gearon or the Electing Offering
         Stockholder proposes to effect the Proposed Transfer (the "Minimum
         Price") and the other material terms and conditions (including, without
         limitation, representations and warranties to be made and any
         indemnification to be provided) on which Gearon or the Electing
         Offering Stockholder proposes to Transfer the Offered Securities. The
         Transfer Notice shall contain an affirmation by Gearon or the Electing
         Offering Stockholder that it has a reasonable expectation of being able
         to effect a Transfer of the Offered Securities at the Minimum Price and
         on such other terms and conditions to such Third Party or Third Parties
         (or class of Persons), and shall recite the basis for such expectation.
         The Transfer Notice shall constitute an offer (the "First Refusal
         Offer") to Transfer the Offered Securities to Gearon (in the case of a
         proposed Transfer by an Electing Offering Stockholder), Holding (in the
         case of a proposed Transfer by Gearon and, to such extent, if any, that
         the First Refusal Offer is not accepted by Gearon, by an Electing
         Offering Stockholder), and, to such extent, if any, that the First
         Refusal Offer is not accepted by Holding, to Transfer the Offered
         Securities to ATC, in each case in accordance with this Section, for a
         cash price equal to one hundred percent (100%) of the Minimum Price and
         on other terms and conditions, if any, no less favorable to Gearon (in
         the case of a proposed Transfer by an Electing Offering Stockholder),
         Holding and ATC than those proposed to be offered to such Third Party
         or Third Parties (or class of Persons). If any portion of the
         consideration to be paid to Gearon or an Electing Offering Stockholder
         in the Proposed Transfer shall consist of assets other than cash, in
         determining the price the Offered Securities are to be offered to
         Gearon (in the case of a proposed Transfer by an Electing Offering
         Stockholder), Holding and ATC, the fair cash value of such assets shall
         be considered.

                  (b) Subject to Section 7(f), in the case of a proposed
         Transfer by an Electing Offering Stockholder, the right of first
         refusal may be exercised by Gearon by delivery of a written notice to
         such Electing Offering Stockholder, Holding and to ATC within twenty
         (20) days after receipt by Gearon of the Transfer Notice (the "Gearon
         Notice Period"), which notice shall state the number of Offered
         Securities Gearon intends to purchase pursuant to this paragraph (b).
         If Gearon fails to respond to an Electing Offering Stockholder within
         the Gearon Notice Period, the failure shall be deemed a rejection by
         Gearon of the First Refusal Offer.

                  (c) Subject to Section 7(f), the right of first refusal may be
         exercised by Holding by delivery of a written notice to Gearon or an
         Electing Offering Stockholder and to ATC within

                                       -7-

<PAGE>

         twenty (20) days after receipt by Holding of the Transfer Notice (the
         "Holding Notice Period"), which notice shall state the number of
         Offered Securities Holding intends to purchase pursuant to this
         paragraph (c). If Holding fails to respond to Gearon or an Electing
         Offering Stockholder within the Holding Notice Period, the failure
         shall be deemed a rejection by Holding of the First Refusal Offer.

                  (d) Subject to Section 7(f), to the extent Holding rejects the
         First Refusal Offer or exercises the right of first refusal with
         respect to fewer than all of the Offered Securities, ATC may exercise
         the First Refusal Offer, by delivery of a written notice to Gearon or
         an Electing Offering Stockholder within the Holding Notice Period with
         respect to the balance or all of the Offered Securities, as applicable.
         If ATC fails to respond to Gearon or an Electing Offering Stockholder
         within the Holding Notice Period, the failure shall be deemed a
         rejection of the First Refusal Offer.

                  (e) If the First Refusal Offer is accepted in its entirety by
         Gearon, Holding and/or ATC, the purchase of the Offered Securities by
         Gearon, Holding and/or ATC pursuant to this Section shall take place at
         10:00 a.m., local time, at the principal executive offices of ATC, on
         such date within thirty (30) days after the expiration of the Holding
         Notice Period as Gearon, Holding and/or ATC shall notify Gearon or an
         Electing Offering Stockholder of in writing at least five (5) days
         prior to such closing, on the terms and conditions of the Proposed
         Transfer, and Gearon, Holding and/or ATC and Gearon or an Electing
         Offering Stockholder shall enter into a securities purchase agreement
         containing the Minimum Price and the other terms and conditions set
         forth in the Proposed Transfer. The Minimum Price for the Offered
         Securities purchased by Gearon, Holding and ATC shall be paid by wire
         transfer to Gearon or an Electing Offering Stockholder against receipt
         of a certificate or certificates representing all Offered Securities so
         purchased, properly endorsed for transfer, free and clear of all Liens.
         If the Gearon Note or any note from any Electing Offering Stockholder
         is not paid in full at the closing, Holding and/or ATC shall be
         entitled to apply the purchase price to the payment of a principal
         amount of the Gearon Note or any such other note, as applicable, in an
         amount determined by (i) multiplying the Minimum Price by (ii) a
         fraction (x) the numerator of which is the number of Offered Securities
         and (y) the denominator of which is the number of Holding Securities
         owned by Gearon or the Electing Offering Stockholder, as applicable,
         immediately prior to such Transfer, and Gearon or the Electing Offering
         Stockholder, as applicable, shall pay all accrued and unpaid interest
         on such principal amount to the closing. At the election of ATC, the
         Holding Securities, if any, to be purchased by it may be acquired in
         the name of one or more nominees (whether or not any such nominee is an
         Affiliate of ATC); provided, however, that any such nominee is
         designated by written notice given at least five (5) days prior to the
         date of closing.

                  (f) Any purchase of the Offered Securities by Gearon, Holding
         and/or ATC pursuant to this Section shall be conditioned (by Gearon or
         an Electing Offering Stockholder) upon Gearon, Holding and/or ATC
         exercising in the aggregate the right of first refusal with respect to
         all of the Offered Securities.

                  (g) Notwithstanding anything to the contrary contained herein,
         if Gearon, Holding and/or ATC have not exercised the right of first
         refusal with respect to all of the Offered Securities pursuant to this
         Section, then Gearon or an Electing Offering Stockholder may, subject
         to the provisions of Section 5, Transfer to the Third Party or Third
         Parties specified in the Notice (or to a member of the class of Persons
         described in the Notice) (the "Third Party Transferee") on the terms
         and conditions of the Proposed Transfer all but not less than all of
         the Offered Securities; provided, however, that such sale is
         consummated within ninety (90) days from the expiration of

                                       -8-

<PAGE>

         the Holding Notice Period; and provided further, however, that such
         Third Party Transferee shall agree, in writing, in advance with Gearon,
         Holding and ATC to be bound by and to comply with all applicable
         provisions of this Agreement to the same extent as if such Third Party
         Transferee were Gearon or an Electing Offering Stockholder, as
         applicable. If such sale is not consummated within such ninety (90)-day
         period, the restrictions provided for in this Section shall again
         become effective, and no Transfer of such Offered Securities may be
         made thereafter without again offering the same to Gearon, Holding and
         ATC in accordance with the terms and conditions of this Agreement. Any
         reduction in the Minimum Price or any material change in any of the
         other material terms and conditions of the Proposed Transfer favorable
         to the Third Party Transferee shall constitute a new Proposed Transfer
         and shall require Gearon or an Electing Offering Stockholder to comply
         with all of the provisions of this Section. It shall be a condition to
         the consummation of any Transfer of Offered Securities by Gearon to any
         Third Party Transferee pursuant to the provisions of this Section that
         Gearon shall have repaid a principal amount of the Gearon Note in an
         amount determined by (i) multiplying the cash proceeds (or the fair
         cash value of any non-cash proceeds) by (ii) a fraction (x) the
         numerator of which is the number of Offered Securities and (y) the
         denominator of which is the number of Holding Securities owned by
         Gearon immediately prior to such Transfer, together with all accrued
         and unpaid interest on such principal amount to the closing.

                  (h) The provisions of this Section shall not apply to any
         Transfer by Gearon or an Electing Offering Stockholder pursuant to
         Section 6.

         Section 8. Holding Stock Option Plan. Holding and ATC, jointly and
                    -------------------------
severally, covenant and agree that Holding will, as soon as reasonably
practicable, adopt the Plan which will contain terms and conditions comparable
to those of the 1997 Stock Option Plan, as amended, of ATC, except as follows:

                  (a) Number of Shares. The Plan will cover a number of shares
                      ----------------
         of Holding Common Stock equal to three and six-tenths percent (3.6%) of
         the number of shares of Holding Common Stock to be outstanding on a pro
         forma basis assuming all shares covered by the Plan were issued and
         outstanding.

                  (b) Prospective Optionees. Options will be granted from time
                      ---------------------
         to time to such individuals as may, from time to time, be an officer,
         employee or independent consultant or adviser to Holding and are
         approved by the Holding Board. ATC hereby approves the individuals
         listed in Schedule A attached hereto and made a part hereof as eligible
         to acquire Options.

                  (c) Certain Option Terms. Options will not, except as
                      --------------------
         hereinafter provided, vest prior to July 1, 2006, at which time they
         will vest in their entirety, will be subject to earlier vesting under
         certain circumstances, including the exercise by Gearon of the put
         pursuant to the provisions of Section 6(a) or the exercise by ATC of
         the call pursuant to the provisions of Section 6(b)(i), and will be
         cancelled in its entirety upon the termination of the optionee for
         cause or his terminating his employment other than for good reason.

                  (d) Noncompetition Agreements. It will be a condition of any
                      -------------------------
         grant of Options under the Plan that the optionee execute and deliver
         to Holding, a noncompetition agreement substantially in the form of the
         Gearon Noncompetition Agreement, modified, to the extent deemed
         reasonably necessary by Holding, to ensure compliance with Mexican law.

         Section 9. Miscellaneous Provisions.
                    -------------------------

                                       -9-

<PAGE>

         (a) Termination. This Agreement shall continue until, and shall
             ------------
terminate immediately upon, (a) execution of a written agreement of termination
by (i) ATC and (ii) Gearon, so long as he or any member of the Gearon Group owns
any Holding Common Stock, or, at such time as no member of the Gearon Group owns
any Holding Common Stock, a majority in interest of the other Stockholders (on a
fully diluted basis) or (b) ATC (and/or its Affiliates) owning all of the
outstanding shares of Holding Common Stock.

         (b) Expenses. Whether or not the transactions contemplated hereby shall
             --------
be consummated, each party will pay all of its respective expenses in connection
with such transactions and in connection with any amendments or waivers (whether
or not the same become effective) under or in respect of this Agreement.

         (c) Assignment; Successors and Assigns. This Agreement shall not be
             ----------
assignable by any party and any such assignment shall be null and void, except
that it shall inure to the benefit of and be binding upon any successor to any
party by operation of Law, including by way of merger, consolidation or sale of
all or substantially all of its assets, and any of the parties may assign its
rights and remedies hereunder to any bank or other financial institution that
has loaned funds or otherwise extended credit to it or any of its Affiliates.
This Agreement shall be binding upon and inure solely to the benefit of the
parties and their permitted successors and assigns, and nothing in this
Agreement, express or implied, is intended to or shall confer upon any person
any right, benefit or remedy of any nature whatsoever under or by reason of this
Agreement, except as otherwise provided in this Section.

         (d) Notices and Communications. All notices and other communications
             --------------------------
which by any provision of this Agreement are required or permitted to be given
shall be given in writing and shall be effective (i) five (5) days after being
mailed by first-class, express mail, postage prepaid, (ii) the next day when
sent by overnight by a nationally recognized overnight mail courier service,
(iii) upon confirmation when sent by telegram, telecopy or other similar form of
rapid transmission, confirmed by mailing (by first class or express mail,
postage prepaid, or nationally recognized overnight mail courier service)
written confirmation at substantially the same time as such rapid transmission,
or (iv) upon delivery personally delivered to the receiving party (if an
individual) or an officer or other responsible individual of the receiving
party. All such communications shall be mailed, set or delivered as set forth
below or at such other addresses as the party entitled thereto shall have
designated by notice as herein provided.

                  (i) if to Holding or ATC, at 116 Huntington Avenue, Boston,
         Massachusetts 02116 Attention: Chief Executive Officer and Chief
         Financial Officer, Telecopier No.: (617) 375-7575 with a copy (which
         shall not constitute notice to ATC or Holding) to Sullivan & Worcester
         LLP, One Post Office Square, Boston, Massachusetts 02109, Attention:
         William J. Curry, Esq., Telecopier No.: (617) 338-2880);

                  (ii) if to Gearon, at 3200 Cobb Galleria Parkway, Suite 205,
         Atlanta, Georgia 30339, Telecopier No: (770) 952-4999 with a copy
         (which shall not constitute notice to Gearon) to King & Spalding, 1185
         Avenue of the Americas, New York, New York 10036, Attention: John L
         Graham, Esq., Telecopier No.: (212) 556-2222); and

                  (iii) if to any other Stockholder, at his address as it
         appears on the stock register of Holding.

         (e) Amendments and Waivers. Changes in or additions to this Agreement
             ----------------------
may be made, or compliance with any term, covenant, agreement, condition or
provision set forth herein may be omitted or waived (either generally or in a
particular instance and either retroactively or prospectively) with, but only

                                       -10-

<PAGE>

with, the consent in writing of the parties hereto. No delay on the part of any
party at any time or times in the exercise of any right or remedy shall operate
as a waiver thereof. Any consent may be given subject to satisfaction of
conditions stated therein. The failure to insist upon the strict provisions of
any covenant, term, condition or other provision of this Agreement or to
exercise any right or remedy thereunder shall not constitute a waiver of any
such covenant, term, condition or other provision thereof or default in
connection therewith. The waiver of any covenant, term, condition or other
provision thereof or default thereunder shall not affect or alter this Agreement
in any other respect, and each and every covenant, term, condition or other
provision of this Agreement shall, in such event, continue in full force and
effect, except as so waived, and shall be operative with respect to any other
then existing or subsequent default in connection therewith.

         (f) Governing Law. The validity, interpretation, construction and
             -------------
performance of this Agreement shall be governed by, and construed in accordance
with, the applicable Laws of the United States of America and the Laws of the
State of Delaware applicable to contracts made and performed in such State and,
in any event, without giving effect to any choice or conflict of laws provision
or rule that would cause the application of domestic substantive laws of any
other jurisdiction.

         (g) Entire Agreement. This Agreement (including the Exhibits)
             ----------------
constitutes the entire agreement among the parties hereto with respect to the
subject matter hereof and supersedes all prior agreements, arrangements,
covenants, promises, conditions, understandings, inducements, representations
and negotiations, expressed or implied, oral or written, between them as to such
subject matter.

         (h) Specific Performance; Other Rights and Remedies. Each party
             -----------------------------------------------
recognizes and agrees that in the event any other party should refuse to perform
any of its obligations under this Agreement, the remedy at law would be
inadequate and agrees that for breach of such provisions, each party shall be
entitled to injunctive relief and to enforce its rights by an action for
specific performance to the extent permitted by Applicable Law. Each party
hereby waives any requirement for security or the posting of any bond or other
surety in connection with any temporary or permanent award of injunctive,
mandatory or other equitable relief. Nothing herein contained shall be construed
as prohibiting each party from pursuing any other remedies available to it
pursuant to the provisions of, and subject to the limitations contained in, this
Agreement for such breach or threatened breach.

         (i) Saturdays, Sundays, Holidays, etc. If the last or appointed day for
             ---------------------------------
taking of any action required or permitted hereby shall be day other than a
Business Day, then such action may be taken on the next succeeding Business Day.

         (j) Headings; Counterparts. The headings contained in this Agreement
             ----------------------
are for reference purposes only and shall not limit or otherwise affect the
meaning of any provision of this Agreement. This Agreement may be executed in
any number of counterparts, each of which shall be an original, but all of which
together shall constitute one instrument, binding upon all of the parties
hereto. In pleading or proving any provision of this Agreement, it shall not be
necessary to produce more than one of such counterparts.

         (k) Severability. If any provision of this Agreement shall be held or
             ------------
deemed to be, or shall in fact be, invalid, inoperative, illegal or
unenforceable as applied to any particular case in any jurisdiction or
jurisdictions, or in all jurisdictions or in all cases, because of the conflict
of any provision with any constitution or statute or rule of public policy or
for any other reason, such circumstance shall not have the effect of rendering
the provision or provisions in question invalid, inoperative, illegal or
unenforceable in any other jurisdiction or in any other case or circumstance or
of rendering any other provision or provisions herein contained invalid,
inoperative, illegal or unenforceable to the extent that

                                       -11-

<PAGE>

such other provisions are not themselves actually in conflict with such
constitution, statute or rule of public policy, but this Agreement shall be
reformed and construed in any such jurisdiction or case as if such invalid,
inoperative, illegal or unenforceable provision had never been contained herein
and such provision reformed so that it would be valid, operative and enforceable
to the maximum extent permitted in such jurisdiction or in such case.
Notwithstanding the foregoing, in the event of any such determination the effect
of which is to affect materially and adversely any party, the parties shall
negotiate in good faith to modify this Agreement so as to effect the original
intent of the parties as closely as possible to the fullest extent permitted by
applicable Law in an acceptable manner to the end that the transactions
contemplated by this Agreement are fulfilled and consummated to the maximum
extent possible.

         (l) Further Acts. Each party agrees that at any time, and from time to
             ------------
time, before and after the consummation of the transactions contemplated by this
Agreement, it will do all such things and execute and deliver all such other
agreements, instruments and documents and other assurances, as any other party
or its counsel reasonably deems necessary or desirable in order to carry out the
terms and conditions of this Agreement and the transactions contemplated hereby
or to facilitate the enjoyment of any of the rights created hereby or to be
created hereunder. Without limiting the generality of the foregoing, ATC agrees
to use its reasonable business efforts to secure all consents and approvals
required from its lenders or others holding its debt instruments to the extent
necessary to enable it to perform its obligations under this Agreement,
including without limitation any purchase of the Holding Securities from Gearon
or any other Stockholder.

         (l) Legend on Certificate. Each party acknowledges that no Transfer of
             ---------------------
any of the shares of Holding Common Stock held by it may be made except in
compliance with applicable federal and state securities laws. All the
certificates or other instruments representing any of such shares that are now
or hereafter held by such party shall be subject to the terms of this Agreement
and shall have endorsed in writing, stamped or printed, thereon the following
legend:

         "THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED
         UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY APPLICABLE
         STATE SECURITIES LAWS AND MAY NOT BE TRANSFERRED EXCEPT IN
         COMPLIANCE WITH THOSE LAWS. THE SECURITIES ARE ALSO SUBJECT TO
         CERTAIN RIGHTS AND RESTRICTIONS, INCLUDING BUT NOT LIMITED TO
         RESTRICTIONS ON TRANSFER, SET FORTH IN AN AGREEMENT AMONG THE
         HOLDER, THE CORPORATION AND CERTAIN STOCKHOLDERS OF THE
         CORPORATION, AS AMENDED FROM TIME TO TIME, A COPY OF WHICH IS
         ON FILE WITH AND AVAILABLE FROM THE SECRETARY OF THE
         CORPORATION UPON WRITTEN REQUEST."

         (m) Effectiveness of Transfers. Any Holding Securities transferred by
             --------------------------
any party to this Agreement shall be held by the transferee thereof pursuant to
this Agreement. Such transferee shall, except as otherwise expressly stated
herein, have all the rights and be subject to all of the obligations of its
transferor (including in the case of a Gearon Holder all of those of Gearon)
under this Agreement automatically and without requiring any further act by such
transferee or by any parties to this Agreement. Without affecting the preceding
sentence, if such transferee is not a party to this Agreement on the date of
such Transfer, then such transferee, as a condition to such Transfer, shall
confirm such transferee's obligations hereunder in accordance with Section 9(n).
No Transfer of Holding Securities shall be recorded on Holding's books and
records, and no such Transfer shall be otherwise effective, unless such Transfer
is made in accordance with the terms and conditions of this Agreement, and
Holding is hereby authorized by all of the parties to enter appropriate stop
transfer notations on its transfer records

                                       -12-

<PAGE>

to give effect to this Agreement. No actual or purported Transfer of any Holding
Securities (or any portion thereof), nor any right thereto, whether voluntary or
involuntary, direct or indirect, which is in violation of any provision of this
Agreement shall be valid or effective to grant any Person any right, title or
interest in or to such Holding Securities (or portion thereof) or any rights as
a stockholder of Holding. Anything in this Section or elsewhere in this
Agreement to the contrary notwithstanding, (i) no ATC Holder other than ATC
shall have any obligation under Section 3 or 6, it being the intent of the
parties that any such ATC Holder shall be obligated only under Sections 4 and 9,
but any such ATC Holder may, except as it may have otherwise agreed in writing
with ATC (or any other ATC Holder), exercise the rights of ATC (or any such ATC
Holder) set forth in this Agreement, and (ii) ATC shall remain obligated, to the
greatest extent applicable, under all Sections of this Agreement notwithstanding
any Transfer of all or any part of the Holding Securities owned by it or any of
its Affiliates.

         (n) Additional Stockholders. Any Person acquiring any shares of Holding
             -----------------------
capital stock shall on or before the Transfer or issuance to it of such shares,
sign a counterpart signature page hereto in form reasonably satisfactory to
Holding, Gearon and ATC and shall thereby become a party to this Agreement.
Holding shall require each Person acquiring any shares of capital stock of
Holding or an option, warrant or other right to purchase shares of capital stock
of Holding under any option or other equity participation plan to execute a
counterpart signature page hereto.

         (o) Power of Attorney. Gearon and each other Stockholder hereby
             -----------------
appoints ATC as its agent and attorney-in-fact, which appointment is coupled
with an interest, and is irrevocable, for purposes of executing and delivering
all such agreements, instruments and documents necessary or desirable in order
to effectuate the provisions of this Agreement, including without limitation the
right and power to transfer the Holding Securities of Gearon and such other
Stockholder to ATC in accordance with the provisions of Sections 6 and 7.
Notwithstanding the foregoing, if Gearon or any other Stockholder shall have
given a good faith written notice to ATC specifying in reasonable detail that a
bona fide dispute exists between the parties relating to the potential exercise
of such power of attorney, ATC shall not be entitled to exercise it until
further written notice from Gearon or such other Stockholder or a final,
nonappealable judicial order or decision.

         (p) Mutual Drafting. This Agreement is the result of the joint efforts
             ---------------
of the parties, and each provision hereof has been subject to the mutual
consultation, negotiation and agreement of the parties and there shall be no
construction against any party based on any presumption of that party's
involvement in the drafting thereof. Each of the parties is a sophisticated
legal entity or individual that was advised by experienced counsel and, to the
extent it deemed necessary, other advisors in connection with this Agreement.

         IN WITNESS WHEREOF the parties hereto have executed this Agreement, as
of the date and year first above written.

                                     ATC Mexico Holding Corp.

                                     By: /s/ Joseph L. Winn
                                        ---------------------------------

                                       -13-

<PAGE>

                                    Name:

                                    Title: Chief Financial Officer

                                    American Tower Corporation

                                    By: /s/ Steven B. Dodge
                                       ---------------------------------
                                         Name: Steven B. Dodge
                                         Title:   Chairman and CEO

                                   American Tower International, Inc.

                                   By: /s/ Steven B. Dodge
                                      ---------------------------------
                                       Name: Steven B. Dodge
                                       Title:   Chairman and CEO

                                     /s/ J. Michael Gearon, Jr.
                                     ------------------------------------
                                           J. Michael Gearon, Jr.

                                       -14-

<PAGE>

                                                                      APPENDIX A

          "Adjusted EBITDA" shall mean the excess of (a) the sum of (i) earnings
before taxes, interest, and depreciation and amortization of Holding and (ii)
interest income from the loan to TV Azteca S.A. de C.V. (or from comparable
transactions) over (b) a reasonable allocation of administrative overhead of ATC
and its subsidiaries, to the extent (i) ATC actually provides administrative
services to Holding and (ii) expenses related to such services are not already
deducted from earnings. Adjusted EBITDA shall, unless ATC and Gearon agree on
the amount, be determined by the independent accountants of Holding, whose
determination shall, unless objected to in writing by Gearon within ten (10)
Business Days of the delivery of such determination, be binding and conclusive
on all of the Parties. If Gearon shall so timely object, it shall have the right
to submit the matter to an independent accounting firm reasonably acceptable to
ATC and Gearon whose determination shall be binding and conclusive on all of the
Parties and whose expenses shall be paid by Gearon unless its determination of
Adjusted EBITDA is more than five percent (5%) greater than that determined by
Holding's independent accountants in which event they shall be paid by ATC.

         "Affiliate", when used with respect to any Person, shall mean (a) any
other Person at the time directly or indirectly controlling, controlled by or
under direct or indirect common control with such Person, (b) any other Person
of which such Person at the time owns, or has the right to acquire, directly or
indirectly, five percent (5%) or more on a consolidated basis of the equity or
beneficial interests, (c) any other Person which at the time owns, or has the
right to acquire, directly or indirectly, five percent (5%) or more of any class
of the capital stock or beneficial interests of such Person, (d) any executive
officer or director of such Person, and (e) when used with respect to an
individual, shall include a spouse, any ancestor or descendant, or any other
relative (by blood, adoption or marriage), within the third degree of such
individual. A Person shall be deemed to be "controlled by" any other Person if
such other Person possesses, directly or indirectly, power to direct or cause
the direction of the management or policies of such Person or the disposition of
its assets or properties, whether by stock, equity or other ownership, by
contract, arrangement or understanding, or otherwise.

          "ATC" shall have the meaning given to it in the preamble.

         "ATC Change of Control" shall mean (a) the acquisition, directly or
indirectly, by any Person or group (as such term is used in Section 13(d)(3) of
the Exchange Act), other than any Person who is, as of the date hereof, an
executive officer, director or the holder of five percent (5%) or more of the
aggregate voting power of all classes of common stock of ATC, or any Affiliate
of any such officer, director or holder, or any group of which any such officer,
director, holder or Affiliate is a member, of more than fifty percent (50%), of
the aggregate voting power of all classes of common stock of ATC, (b) Steven B.
Dodge ceasing to act as either the Chairman of the Board of Directors or Chief
Executive Officer of ATC, or (c) Gearon being required to report to any Person
other than Steven B. Dodge, the Holding Board and the ATC Board of Directors.

          "ATC Common Stock" shall mean the Class A Common Stock, par value $.01
per share, of ATC or any publicly traded class of common stock into which such
stock shall have been converted or exchanged pursuant to any recapitalization,
reorganization, merger, consolidation or similar event.

         "ATC Holder(s)" shall mean ATC, ATC International, any Affiliate of ATC
or ATC International to whom any Holding Securities may from time to time be
transferred and any other Person

                                       -15-

<PAGE>

deriving its interest, directly or indirectly, in any Holding Securities from
any of the foregoing, other than any Gearon Holder or other Stockholder.

         "ATC International" shall have the meaning given to it in the preamble.

         "ATC Registration Rights Agreement" shall mean the Amended and Restated
Registration Rights Agreement dated February 25, 1999, as heretofore and
hereafter amended.

         "Authority" shall mean any governmental or quasi-governmental
authority, whether administrative, executive, judicial, legislative or other, or
any combination thereof, including without limitation any federal, state,
territorial, county, municipal or other government or governmental or
quasi-governmental agency, arbitrator, authority, board, body, branch, bureau,
or comparable agency or Entity, commission, corporation, court, department,
instrumentality, mediator, panel, system or other political unit or subdivision
or other Entity of any of the foregoing, whether domestic or foreign.

         "Business Day" shall mean any day, other than a Saturday, Sunday or
legal holiday, on which banks in Atlanta, Georgia and Boston, Massachusetts are
permitted to be open for business.

         "Call Notice" shall have the meaning given to it in Section 6(b).

         "Core Business" shall mean the ownership, operation, construction,
leasing and management of telecommunications towers and related businesses such
as site acquisition and zoning activities, but shall exclude, without
limitation, (a) marketing and sale of equipment and components, (b) providing
integrated satellite and fiber network access services (i.e., teleports), and
(c) engineering services, such as wireless broadband and wireless network design
and implementation; radio frequency network design; drive testing; performance
engineering; technical planning for spectrum license holders; upgrading networks
to 3G; transport engineering; and interconnection and microwave services.

         "Disability" shall mean a condition (mental or physical or both) which,
in the good faith judgment of the Holding Board, renders Gearon, in his capacity
as an executive officer of Holding, and by reason of incapacity (mental or
physical or both) unable to perform properly his duties as such executive
officer for a period of not less than six (6) months during any twenty-four (24)
month period.

         "Electing Offering Stockholder" shall have the meaning given to it in
Section 6(a).

          "Electing Put Stockholder" shall have the meaning given to it in
Section 6(a).

         "Entity" shall mean any corporation, partnership, limited liability
company, trust, unincorporated association, government or any agency or
political subdivision thereof.

         "Fair Market Value" shall mean, with respect to the ATC Common Stock,
(a) the average of the high and low reported sales prices, regular way, or, in
the event that no sale takes place on any day, the average of the reported high
and low bid and asked prices, regular way, in either case as reported on the
principal stock exchange on which such stock is listed, or, if not so listed, on
the Nasdaq National Market System; or (b) if such stock is not so listed, (i)
the average of the high and low bid and high and low asked prices on each such
day in the over-the-counter market as reported by Nasdaq, or (ii) if bid and
asked prices for such security on any day shall not have been reported through
Nasdaq, the average of the bid and asked prices for such day as furnished by any
New York Stock Exchange member firm regularly making a market in such security
selected for such purpose by ATC; in each case for the twenty (20)

                                       -16-

<PAGE>

trading days ending five business days prior to the date as of which such Fair
Market Value is being determined.

         "First Refusal Offer" shall have the meaning given to it in Section
7(a).

         "Forfeiture Event" shall mean any of the following acts (other than as
a result of the death or Disability of Gearon) committed by Gearon:

                  (a) any willful or gross failure or refusal to perform, or any
         willful or gross misconduct in the performance of, any significant
         portion of his obligations, duties and responsibilities as an executive
         officer of Holding, the effect of which has been or reasonably could be
         expected to materially and adversely affect the business of ATC or any
         of its Affiliates, as determined in good faith by the ATC Board of
         Directors, and that (i) is incapable of cure, or (ii) has not been
         cured or remedied as promptly as is reasonably possible (and in any
         event within thirty (30) days) after written notice from the Holding
         Board to Gearon specifying in reasonable detail the nature of such
         failure, refusal or misconduct, or

                  (b) material breach of the provisions of Section 2, 3 or 4 of
         the Gearon Noncompetition Agreement which (i) is incapable of cure, or
         (ii) has not been cured or remedied promptly (and in any event within
         thirty (30) days) after written notice from the Holding Board to Gearon
         specifying in reasonable detail the nature of such breach, or

                  (c) Gearon is convicted of, pleads guilty or nolo contendero
         to any act of fraud, embezzlement or misappropriation or other crime
         involving moral turpitude in connection with his employment by Holding
         or any of its Affiliates intended by Gearon to result in substantial
         personal enrichment and which adversely affects the business of ATC or
         any of its Affiliates, all as determined in good faith by the ATC Board
         of Directors.

         "Gearon" shall have the meaning given to it in the preamble and shall,
to the extent applicable, include his heirs, legal representatives and trustees.

         "Gearon Holder(s)" shall mean any member of the Gearon Group, any
Affiliate of any of the foregoing or any other Person deriving its interest,
directly or indirectly, from any member of the Gearon Group or any Affiliate of
any of the foregoing, other than any ATC Holder.

          "Gearon Group" shall mean (a) Gearon, (b) any spouse, ancestor or
descendant, or other relative (by blood, adoption or marriage, past or present),
within the third degree of Gearon, (c) any Affiliate of any of the individuals
included within clause (a) or (b), and (d) any trust for the benefit of any of
the Persons included within clause (a), (b) or (c).

          "Gearon Notice Period" shall have the meaning given to it in Section
7(b).

         "Gearon Noncompetiton Agreement" shall mean the agreement, of even
date, by and among, Holding, Other Holding, ATC and Gearon.

         "Gearon Note" shall have the meaning given to it in Section 3(b).

         "Gearon Termination Event" shall mean the termination by (a) Gearon of
his employment with Holding other than a termination for Good Reason following
an ATC Change of Control or a Holding Change of Control, or (b) Holding of
Gearon's employment as a result of (i) a Forfeiture Event or (ii) a

                                       -17-

<PAGE>

material breach by Gearon of any material provision of this Agreement, or any of
the Related Documents which (x) is incapable of cure, or (y) has not been cured
or remedied promptly (and in any event within thirty (30) days) after written
notice from the Holding Board to Gearon, specifying in reasonable detail the
nature of such breach.

         "Good Reason" shall mean:

                  (a) the assignment to Gearon of any duties inconsistent in any
         material respect with his position, authority, duties or
         responsibilities as contemplated in Section 4(f) or any other action by
         Holding, Other Holding or their Affiliates that results in a
         diminution, in any material respect, in such position, authority,
         duties or responsibilities; or

                  (b) an ATC Change of Control or a Holding Change of Control;
         or

                  (c) a material reduction in Gearon's compensation or other
         benefits (taking into account the compensation and other benefits from
         all Affiliates of Holding from whom he may, from time to time, receive
         compensation), the result of which is to place Gearon in a materially
         less favorable position as to such compensation and benefits compared
         to other employees of Holding and its Affiliates of similar stature and
         position; or

                  (d) any other failure by Holding or ATC to comply in any
         material respect with any material provision of this Agreement or by
         Other Holding or ATC to comply in any material respect with any
         material provision of the Other Agreement; or

                  (e) the failure of Gearon to be nominated as a director of
         ATC;

that (i) is incapable of cure, or (ii) has not been cured or remedied promptly
(and in any event within thirty (30) days) after written notice to the Holding
Board and ATC from Gearon specifying in reasonable detail the nature of such
assignment, action, reduction or failure.

         "Holding" shall have the meaning given to it in the preamble

         "Holding Board" shall have the meaning given to it in Section 4(a).

         "Holding Change of Control" shall mean the acquisition, directly or
indirectly, by any Person or group (as such term is used in Section 13(d)(3) of
the Exchange Act), other than ATC or any of its subsidiaries or any Person who
is, as of the date hereof, an executive officer, director or the holder of five
percent (5%) or more of the ATC Common Stock, or any Affiliate of any such
officer, director or holder, or any group of which any such officer, director,
holder or Affiliate is a member, of more than fifty percent (50%), of the voting
power of all classes of common stock of Holding.

         "Holding Change of Control Notice" shall have the meaning given to it
in Section 6(d).

         "Holding Change of Control Transaction" shall have the meaning given to
it in Section 6(d).

          "Holding Common Stock" shall mean all shares of Common Stock, par
value $.01 per share, of Holding.

         "Holding Notice Period" shall have the meaning given to it in Section
7(c).

                                       -18-

<PAGE>

          "Holding Securities" shall mean all shares of Holding Common Stock
from time to owned by Gearon or any other Person other than the ATC Holders.

         "Holding Value" shall mean the fair market value of the Holding Common
Stock, determined in accordance with this definition. The parties agree that the
fair market value of the Holding Common Stock shall mean the price at which a
willing seller would sell and a willing buyer would buy a comparable business as
an ongoing business in an arm's length transaction (as a sale of the stock or,
if applicable, other equity interests), determined as if Holding were a public
company and the Holding Common Stock were publicly traded on a securities
exchange in the United States of America and widely held at the time of such
determination and without consideration of any restrictions or encumbrances or
contractual rights relating to the equity securities thereof, and assuming all
of the outstanding stock or, if applicable, other equity interests are to be
sold in a single transaction. The Board of Directors of ATC has determined, and
Gearon agrees, that the fair market value of the Holding Common Stock would be
an amount equal to the excess, if any, of (a) fifteen (15) times the Adjusted
EBITDA of Holding for the four fiscal quarters ended prior to the date of
determination over (b) the sum of (i) the aggregate principal amount and accrued
and unpaid interest on all Indebtedness for Money Borrowed of Holding, and (ii)
the aggregate liquidation preference and accrued and unpaid dividends on all
preferred stock of Holding, in each case as of the last day of such four fiscal
quarters. The parties agree that the Board of Directors of ATC shall, from time
to time, determine whether the foregoing valuation methodology is an appropriate
one for determining Holding Value. If the ATC Board of Directors determines,
after consultation with Gearon, that such valuation methodology no longer
reflects the fair market value of the Holding Common Stock, it shall (a)
determine such fair market value, (b) establish new valuation methodology, or
(c) establish other means for determining it, including without limitation by
the appointment of an investment banking firm knowledgeable in the business in
which Holding is engaged and reasonably acceptable to Gearon or, in the event
they are unable to agree upon a single investment banking firm, each shall
appoint one such firm and the two firms thus appointed shall select a third firm
whose determination of such fair market value shall be binding and conclusive on
the parties. Any such investment banking firm shall determine such fair market
value based on the then existing facts and circumstances, including the existing
business plan and projections of Holding. Holding shall pay all costs and
expenses of any investment banking firm appointed pursuant to these provisions.
ATC shall promptly advise Gearon of its determination. If the ATC Board of
Directors makes a determination or establishes a new valuation methodology and
such determination or valuation methodology results in a lower Holding Value
than the valuation methodology set forth in this definition, Gearon shall have
the right to have an independent investment banking firm appointed in accordance
with the foregoing provisions of this definition. Anything in this definition to
the contrary notwithstanding, for purposes of determining the fair market value
of the Holding Common Stock, it shall be assumed that, and the valuation shall
be based on the assumption that, the only business conducted by Holding was the
Core Business. Without limiting the generality of the foregoing, there shall be
excluded from the revenues and expenses of Holding for purposes of determining
Holding Value all revenues and expenses (including without limitation any
increased administrative costs, incremental taxes, and exchange rate
fluctuations) attributable to any business that is not a Core Business and, to
the extent that any item of revenue or expense is not specifically related to a
Core or non-Core Business (e.g., revenue and expenses attributable to a
"bundled" agreement), it shall be equitably allocated to each in accordance with
generally accepted accounting principles.

         "Indebtedness for Money Borrowed" shall mean money borrowed and
indebtedness represented by notes payable and drafts accepted representing
extensions of credit, all obligations evidenced by bonds, debentures, notes or
other similar instruments, the maximum amount currently or at any time
thereafter available to be drawn under all outstanding letters of credit issued
for the account of such Person, all indebtedness upon which interest charges are
customarily paid by such Person, and all

                                       -19-

<PAGE>

indebtedness (including capitalized lease obligations) issued or assumed as full
or partial payment for property or services, whether or not any such notes,
drafts, obligations or indebtedness represent Indebtedness for Money Borrowed,
but shall not include (a) trade payables, (b) expenses accrued in the ordinary
course of business, or (c) customer advance payments and customer deposits
received in the ordinary course of business.

         "Law" shall mean any (a) administrative, judicial, legislative or other
action, code, consent decree, constitution, decree, directive, enactment,
finding, law, injunction, interpretation, judgment, order, ordinance, policy
statement, proclamation, promulgation, regulation, requirement, rule, rule of
law, rule of public policy, settlement agreement, statute, or writ of any
Authority, domestic or foreign; or (b) the common law, or other legal precedent.

          "Lien" shall mean any of the following: mortgage, lien (statutory or
other), or other security agreement, arrangement or interest; hypothecation,
pledge or other deposit arrangement; assignment; charge; levy; executory
seizure; attachment; garnishment; encumbrance (including any easement,
exception, reservation or limitation, right of way, and the like); conditional
sale, title retention or other similar agreement, arrangement, device or
restriction; preemptive or similar right; any financing lease involving
substantially the same economic effect as any of the foregoing; the filing of
any financing statement under the Uniform Commercial Code or comparable law of
any jurisdiction; restriction on sale, transfer, assignment, disposition or
other alienation; or any option, equity, claim or right of or obligation to, any
other Person, of whatever kind and character.

         "Minimum Price" shall have the meaning given to it in Section 7(a).

          "Noncompetition Agreement" shall mean the noncompetition agreement,
dated as of the date hereof, in the form of Exhibit C hereto.

          "Offered Securities" shall have the meaning given to it in Section
7(a).

         "Option(s)" shall have the meaning given to it in the second Whereas
paragraph.

         "Other Agreement" shall mean the agreement, of even date, by and among
Other Holding, ATC, ATC International, and Gearon.

         "Other Holding" shall mean ATC South America Holding Corp., a Delaware
corporation owned by ATC and Gearon in the same proportions as ATC and Gearon
own Holding.

         "Other Note" shall mean the note attached to the Other Agreement as
Exhibit A.

         "Other Pledge Agreement" shall mean the pledge agreement attached to
the Other Agreement as Exhibit B.

         "Permitted Transfer" shall mean:

                  (a) a Transfer of any Holding Securities (other than an
         Option) by Gearon or any other Stockholder who is a natural person and
         such Person's spouse, children, parents or siblings (whether natural,
         step or by adoption) or to a trust solely for the benefit of one or
         more of any of such Persons, so long as such Person is the sole trustee
         of such trust;

                  (b) a Transfer of Holding Securities between or among the
         Stockholders ; and

                                       -20-

<PAGE>

                  (c) a Transfer of Holding Securities between Gearon or any
         other Stockholder who is a natural person and such Person's legal
         representatives, guardians or conservators.

No Permitted Transfer shall be effective unless and until the transferee of the
Holding Securities so transferred executes and delivers to Holding an executed
counterpart of this Agreement pursuant to the provisions of Section 9(n).

         "Permitted Transferee" shall mean any Person who shall have acquired
and who shall hold any Holding Securities pursuant to a Permitted Transfer, and
shall include the Persons listed on Schedule A attached hereto so long as they
are employees of Holding or any Affiliate of Holding.

         "Person" means an individual or Entity.

         "Plan" shall have the meaning given to it in the second Whereas
paragraph.

          Pledge Agreement" means the Pledge Agreement attached to this
Agreement as Exhibit B.

          "Proposed Transfer" shall have the meaning given to it in Section 7.

         "Put/Call Price" shall mean, with respect to Holding Securities owned
by any Stockholder, the amount derived by multiplying (i) the Holding Value by
(ii) a fraction (x) the numerator of which is the number of shares of Holding
Common Stock represented by the Holding Securities held by such Stockholder and
(y) the denominator of which is the aggregate number of shares of Holding Common
Stock at the time outstanding.

         "Put Notice" shall have the meaning given to it in Section 5(a).

         "Related Documents" shall mean the Other Agreement, the Note, the Other
Note, the Noncompetition Agreement, the Pledge Agreement, and the Other Pledge
Agreement.

         "Stockholder(s)" shall have the meaning given to it in the preamble.

          "Third Party" means any Person other than Holding or ATC (or any of
its Affiliates).

         "Third Party Transferee" shall have the meaning given to it in Section
7(g).

         "Transfer" shall mean to transfer, issue, sell, assign, pledge,
hypothecate, give, grant or create a security interest in or lien on, place in
trust (voting or otherwise), assign an interest in or in any other way encumber
or dispose of, directly or indirectly and whether or not by operation of law or
for value, any of the Holding Securities.

         "Transfer Notice" shall have the meaning given to it in Section 7(a).

                                       -21-<PAGE>

                                                                   Exhibit 10.29
                                                                   -------------

                  NONCOMPETITION AND CONFIDENTIALITY AGREEMENT

     This Agreement (this "Agreement") made as of October 11, 2001, by and
between American Tower Corporation, a Delaware corporation ("ATC"), and J.
Michael Gearon, Jr. ("Gearon"), an individual residing at 2995 Paces Lake Court,
Atlanta, Georgia 30339.

     WHEREAS, ATC, American Tower International, Inc., a Delaware corporation
("ATC International"), Gearon, and ATC Mexico Holding Corp, a Delaware
corporation ("ATC Mexican Sub"), are parties to a Stockholder Agreement, dated
as of the date hereof (the "Mexican Stockholder Agreement"), pursuant to which
ATC Mexican Sub will issue and sell to Gearon shares of its Common Stock, par
value $.01 per share; and

     WHEREAS, ATC, ATC International, Gearon, and ATC South America Holding
Corp, a Delaware corporation ("ATC South American Sub"), may become parties to a
Stockholder Agreement (the "South American Stockholder Agreement" and,
collectively with the Mexican Stockholder Agreement, the "Stockholder
Agreements"), pursuant to which ATC South American Sub will issue and sell to
Gearon South America shares of its Common Stock, par value $.01 per share; and

     WHEREAS, Gearon is one of the executive officers of ATC and will become the
president of ATC Mexican Sub and ATC South American Sub;

     NOW, THEREFORE, in consideration of the consummation of the transactions
contemplated by the Stockholder Agreements and the election of Gearon as
president of ATC Mexican Sub and ATC South American Sub, the sum of One Dollar
($1.00), the material covenants and agreements contained herein, and other good
and valuable consideration, the receipt, adequacy and sufficiency of which are
hereby acknowledged, the parties hereto, intending to be legally bound, do
covenant and agree as follows:

     Section 1. Definitions. Terms used in this Agreement which are not defined
herein but which are defined in the Stockholder Agreements shall have the
respective meanings so defined.

     Confidential Information shall mean any and all information (excluding
information in the public domain other than as a direct or indirect result of
any breach by Gearon or either Gearon Entity of the provisions of this
Agreement) related to the business, operations, management, assets, property,
plans or prospects, condition, financial or other, or results of operation of
ATC, any Affiliate of ATC or any of their respective successors or assigns,
including without limitation:

     (a)  the whole or any portion or phase of any business plans, financial
          information, purchasing data, supplier or customer data, accounting
          data, or computer programs (including source and object codes), tapes,
          discs, data, software or other information;

     (b)  the whole or any portion or phase of any marketing or sales
          information or technique, sales records, customer lists, supplier
          lists, prices, sales projections or other listings of names,
          addresses, or telephone numbers, or other sales information;

     (c)  the whole or any portion or phase of any employee payroll, fringe
          benefit, salary, bonus, commission or other form of compensation
          information and all employee personnel information, including
          information relating to performance evaluations, discipline, employee
          conduct, complaints and other matters relating to employment of any
          Person; and

<PAGE>

     (d)  Intellectual Property;

whether or not any of the foregoing has been made, developed and/or conceived by
Gearon or by others in the employ of any such Person. Notwithstanding the
foregoing, the term "Confidential Information" shall not include and information
reasonably necessary for the conducting of any activity expressly excluded from
the definition of "Proscribed Activity" hereunder.

     Covered Territory shall mean (a) while Gearon is employed by ATC or any of
its Affiliates, North, South and Latin America, Europe and all other areas in
which ATC or any of its Affiliates has invested or proposes to invest; and (b)
thereafter, North America and any other markets where Gearon has been or is
involved or is negotiating a proposed investment, acquisition or other
transaction on behalf of ATC or any of its Affiliates.

     Good Reason shall mean:

     (a)  the assignment to Gearon of any duties inconsistent in any material
          respect with his position, authority, duties or responsibilities as
          contemplated in Section 4(f) of the Stockholder Agreement or any other
          action by ATC, ATC Mexican Sub or ATC South American Sub or any of
          their Affiliates that results in a diminution, in any material
          respect, in such position, authority, duties or responsibilities; or

     (b)  a material reduction in Gearon's compensation or other benefits
          (taking into account the compensation and other benefits from ATC, ATC
          Mexican Sub or ATC South American Sub and their Affiliates from whom
          he may, from time to time, receive compensation), the result of which
          is to place Gearon in a materially less favorable position as to such
          compensation and benefits compared to other employees of ATC, ATC
          Mexican Sub or ATC South American Sub and their Affiliates of similar
          stature and position; or

     (c)  any other failure by ATC, ATC Mexican Sub or ATC South American Sub or
          any of their Affiliates to comply in any material respect with any
          material provision of either Stockholder Agreement; or

     (d)  the failure of Gearon to be nominated as a director of ATC;

that (i) is incapable of cure, or (ii) has not been cured or remedied promptly
(and in any event within thirty (30) days) after written notice to the board of
directors of ATC from Gearon specifying in reasonable detail the nature of such
assignment, action, reduction or failure.

     Immediate Family shall mean spouses, children and parents, whether related
by blood, adoption or marriage.

     Intellectual Property shall mean, with respect to Gearon, any and all
research, information, inventions, designs, procedures, developments,
discoveries, improvements, patents and applications therefor, trademarks and
applications therefor, service marks, trade names, copyrights and applications
therefor, trade secrets, drawing, plans, systems, methods, specifications,
computer software programs, tapes, discs and related data processing software
(including object and source codes) owned by Gearon or in which he has an
interest and all other manufacturing, engineering, technical, research and
development data and know-how made, conceived, developed and/or acquired by
Gearon solely or jointly with others during the period of his employment with
ATC or any of its Subsidiaries or within one year thereafter, which relate to
the manufacture, production or processing of any products developed or sold by
ATC or any of its Subsidiaries during the term of this Agreement or which are
within the scope of or usable in

                                       -2-

<PAGE>

connection with ATC's or any of its Subsidiaries' business as it may, from time
to time, hereafter be conducted or proposed to be conducted.

     Proscribed Activity shall mean any and all activities related to (a) the
construction, ownership, operation, leasing or management of telecommunications
or broadcast towers, (b) providing network development services or components
for wireless service providers or broadcasters, (c) providing high speed
Internet access and related services via satellite to foreign-based Internet
service providers, telephone or other telecommunciations companies, and other
businesses, or (d) providing other satellite and Internet protocol network
transmission services.

     Restricted Period shall mean a period commencing with the date hereof and
terminating the latest of (a) one year after the later of (i) exercise of the
put (or call) provided for in Section 6 of the Mexican Stockholder Agreement or
(ii) exercise of the put (or call) provided for in Section 6 of the South
American Stockholder Agreement, (b) two years after the sooner to occur of (i) a
Forfeiture Event, or (ii) the resignation by Gearon from all positions with ATC
and each of its subsidiaries other than for Good Reason, or (c) one year after
the resignation by Gearon from all positions with ATC and each of its
subsidiaries for the reason set forth in paragraph (d) of the definition of Good
Reason.

     Section 2. Confidentiality. Gearon shall not, either during the Restricted
Period or thereafter, reveal or disclose to any person outside ATC and its
subsidiaries or use for his own benefit, without ATC's specific prior written
authorization, whether by private communication or by public address or
publication or otherwise, any Confidential Information. All originals and copies
of any Confidential Information, relating to the business of ATC or any of its
subsidiaries, however and whenever produced, shall be the sole property of ATC
and its subsidiaries, not to be removed from the premises or custody of ATC or
its subsidiaries without in each instance first obtaining prior written consent
or authorization of ATC.

     Section 3. Disclosure and Assignment of Intellectual Property. Gearon shall
promptly disclose to ATC and any successor or assign, and grant to ATC, and its
successors and assigns (without any separate remuneration or compensation other
than that received by him from time to time in the course of his employment) his
entire right, title and interest throughout the world in and to all Intellectual
Property. It is understood and agreed that Gearon has heretofore disclosed to
ATC, and assigned to it, all Intellectual Property now known to him over which
he has any control. Gearon agrees to execute all appropriate patent applications
securing all United States and foreign patents on all Intellectual Property, and
to do, execute and deliver any and all acts and instruments that may be
necessary or proper to vest all Intellectual Property in ATC or its nominee or
designee and to enable ATC, or its nominee or designee, to obtain all such
patents; and Gearon agrees to render to ATC, or its nominee or designee, all
such reasonable assistance as it may require in the prosecution of all such
patent applications and applications for the reissue of such patents, and in the
prosecution or defense of all interferences which may be declared involving any
of said patent applications or patents, but the expense of all such assignments
and patent applications, or all other proceedings referred to herein above,
shall be borne by ATC. Gearon shall be entitled to fair and reasonable
compensation for any such assistance requested by ATC or its nominee or designee
and furnished by him after the termination of his employment.

     Section 4. Restriction. ATC through its subsidiaries intends to continue
and expand the business heretofore conducted by it and them and it and in
connection therewith ATC and its subsidiaries have invested and may in the
future be required to invest substantial sums of money, directly or indirectly,
and as Gearon recognizes that ATC would be substantially injured by Gearon
disclosing to others, or by Gearon using for his own benefit, any Intellectual
Property or any other Confidential Information he has obtained or shall obtain
from ATC or any of its subsidiaries, or which he may now

                                       -3-

<PAGE>

possess and which he has made available to ATC or any of its subsidiaries,
Gearon agrees that during the Restricted Period:

     (a)  Neither he nor any member of his Immediate Family will be interested,
          directly or indirectly, as an investor in any other Entity (including
          without limitation either Gearon Entity), business or enterprise
          within the Covered Territory, which is engaged in any Proscribed
          Activity (except as an investor in securities (i) issued by ATC or any
          of its subsidiaries or (ii) listed on a national securities exchange
          or actively traded over the counter so long as such investments are in
          amounts not significant as compared to his total investments and do
          not exceed one percent (1%) of the outstanding securities of the
          issuer of the same class or issue); and

     (b)  Other than in connection with his serving as an officer and/or
          director of ATC and its subsidiaries, he will not, directly or
          indirectly, for his own account or as employee, officer, director,
          partner, trustee, principal, member, joint venturer, agent, adviser,
          consultant or otherwise, engage within the Covered Territory, in any
          phase of any Proscribed Activity.

     Gearon further agrees that during the Restricted Period, he will not,
directly or indirectly, solicit business for a Proscribed Activity from any
Person, business or enterprise which is, or proposes to be, a customer of ATC or
any of its subsidiaries or any of their respective successors or assigns, or
from any Person, business or enterprise with which ATC or any of its
subsidiaries or any of their respective successors or assigns is negotiating or
holding discussion or to which it has made a proposal at the time of such
termination, induce any such Person, business or enterprise not to undertake, or
to curtail or cancel business with ATC or any of its subsidiaries or any of
their respective successors or assigns, induce or attempt to induce any employee
of ATC or any of its subsidiaries or any of their respective successors or
assigns to terminate his employment therewith, or intentionally divulge or
utilize for the direct or indirect benefit (financial or other) of himself or
any other Person, business or enterprise, any Intellectual Property or any
Confidential Information he has obtained as an officer, director and/or
stockholder of ATC or any of its subsidiaries.

     This Agreement shall be deemed to consist of a series of separate
covenants, one for each line of business carried on by ATC and its subsidiaries
and each region included within the geographic areas referred to in this
Section. Gearon and ATC are of the belief that the Restricted Period, the
Proscribed Activity and the Covered Territory herein specified are reasonable,
in light of the circumstances as they exist on the date upon which this
Agreement has been executed, including without limitation the nature of the
business in which ATC and its subsidiaries are engaged and proposes to engage,
the state of their product development and Gearon's knowledge of such business
and his prior affiliations with and interest in ATC. However, if such period,
activity or area should be adjudged unreasonable in any Legal Action, whether at
law or in equity, then the Restricted Period shall be reduced by such period of
time, the Proscribed Activity shall be reduced by such activities, or the
Covered Territory shall be reduced by such area, or any combination thereof, as
are deemed unreasonable, so that this covenant may be enforced in such area,
with respect to such activities and during such period of time as is adjudged to
be reasonable.

     Section 5. Security for Gearon Obligations. Gearon's obligations under this
Agreement shall be secured by twenty percent (20%) of the gross sale proceeds
(before deduction of commissions, discounts, brokerage fees or other fees and
expenses) of (a) all of his membership interests in each Gearon Entity, (b) all
shares of capital stock and other securities issued by ATC Mexican Sub or ATC
South American Sub to Gearon, and (c) all shares of capital stock and other
securities issued by ATC Mexican Sub or ATC South American Sub received by
Gearon pursuant to any distribution to him by either Gearon Entity or otherwise
acquired by him. Gearon and ATC agree that all such proceeds shall be held

                                       -4-

<PAGE>

by an escrow agent or agents reasonably acceptable to Gearon and ATC and subject
to the terms and conditions of an escrow agreement to be executed by ATC and
Gearon and reasonably satisfactory to ATC and Gearon.

     Section 6. Miscellaneous Provisions.

     (a)  Assignment; Successors and Assigns. In the event that ATC shall be
merged with, or consolidated into, any other Entity, or in the event that it
shall sell and transfer substantially all of its assets to another Entity, the
terms of this Agreement shall inure to the benefit of, and be assumed by, the
Entity resulting from such merger or consolidation, or to which ATC's assets
shall be sold and transferred. This Agreement shall not be assignable by Gearon,
but it shall be binding upon his heirs, executors, administrators and legal
representatives to the extent they constitute members of his Immediate Family.
Nothing in this Agreement expressed or implied is intended to and shall not be
construed to confer upon or create in any person (other than the parties hereto
and their permitted successors and assigns) any rights or remedies under or by
reason of this Agreement.

     (b)  Specific Performance; Other Rights and Remedies. Gearon recognizes and
agrees that ATC's remedy at law for any breach of the provisions of this
Agreement, including without limitation Sections 2, 3, or 4 would be inadequate,
and he agrees that for breach of such provisions, ATC shall, in addition to such
other remedies as may be available to it at law or in equity or as provided in
this Agreement, be entitled to injunctive relief and to enforce its rights by an
action for specific performance to the extent permitted by applicable law.
Without limiting the generality of the foregoing, in the event of a breach or
threatened breach by Gearon of the provisions of this Agreement, ATC shall be
entitled to an injunction restraining Gearon from soliciting employees,
customers or suppliers, or from disclosing, in whole or in part, any
Confidential Information, or from rendering any services to any Person to whom
such information has been disclosed, or is threatened to be disclosed, from
engaging, participating or otherwise being connected with any business described
in Section 3 or from otherwise violating the terms of this Agreement. Nothing
herein contained shall be construed as prohibiting each party from pursuing any
other remedies available to it pursuant to the provisions of, and subject to the
limitations contained in, this Agreement for such breach or threatened breach;
provided, however, that none of the parties shall pursue, and each party hereby
waives, any punitive, indirect, special, incidental, exemplary, consequential or
similar damages arising out of this Agreement (including without limitation
damages for diminution in value and loss of anticipated profits) and the
multiplied portion of damages.

     (c)  Entire Agreement. This Agreement constitutes the entire agreement
between ATC and Gearon with respect to the subject matter hereof, and supersedes
all prior agreements, arrangements, covenants, promises, conditions,
understandings, inducements, representations and negotiations, expressed or
implied, oral or written, among them as to such subject matter.

     (d)  Waivers; Amendments. Any provision of this Agreement to the contrary
notwithstanding, changes in or additions to this Agreement may be made, or
compliance with any term, covenant, agreement, condition or provision set forth
herein may be omitted or waived (either generally or in a particular instance
and either retroactively or prospectively) with, but only with, the consent in
writing of the parties hereto. Any consent may be given subject to satisfaction
of conditions stated therein. The failure to insist upon the strict provisions
of any covenant, term, condition or other provision of this Agreement or to
exercise any right or remedy thereunder shall not constitute a waiver of any
such covenant, term, condition or other provision thereof or default in
connection therewith. The waiver of any covenant, term, condition or other
provision thereof or default thereunder shall not affect or alter this Agreement
in any other respect, and each and every covenant, term, condition or other
provision of this Agreement shall, in such event, continue in full force and
effect, except as so waived, and shall be operative with respect to any other
then existing or subsequent default in connection therewith.

                                       -5-

<PAGE>

     (e)  Notices. All notices and other communications which by any provision
of this Agreement are required or permitted to be given shall be given in
writing and shall be effective (i) five (5) days after being mailed by
first-class, express mail, postage prepaid, (ii) the next day when sent by
overnight by recognized mail courier service, (iii) upon confirmation when sent
by telex, telegram, telecopy or other similar form of rapid transmission,
confirmed by mailing (by first class or express mail, postage prepaid, or
recognized overnight mail courier service) written confirmation at substantially
the same time as such rapid transmission, or (iv) upon delivery personally
delivered to an officer of the receiving party. All such communications shall be
mailed, set or delivered as set forth below or at such other addresses as the
party entitled thereto shall have designated by notice as herein provided.

          (i)  if to Holding or ATC, at 116 Huntington Avenue, Boston,
     Massachusetts 02116 Attention: Chief Executive Officer and Chief Financial
     Officer, Telecopier No.: (617) 375-7575 with a copy (which shall not
     constitute notice to ATC or Holding) to Sullivan & Worcester LLP, One Post
     Office Square, Boston, Massachusetts 02109, Attention: William J. Curry,
     Esq., Telecopier No.: (617) 338-2880) and

          (ii) if to Gearon, at 3200 Cobb Galleria Parkway, Suite 205, Atlanta,
     Georgia 30339 with a copy (which shall not constitute notice to Gearon) to
     King & Spalding, 1185 Avenue of the Americas, New York, New York 10036,
     Attention: John L. Graham, Esq., Telecopier No.: (212) 556-2222).

     (f)  Severability. If any provision of this Agreement shall be held or
deemed to be, or shall in fact be, invalid, inoperative, illegal or
unenforceable as applied to any particular case in any jurisdiction or
jurisdictions, or in all jurisdictions or in all cases, because of the
conflicting of any provision with any constitution or statute or rule of public
policy or for any other reason, such circumstance shall not have the effect of
rendering the provision or provisions in question invalid, inoperative, illegal
or unenforceable in any other jurisdiction or in any other case or circumstance
or of rendering any other provision or provisions herein contained invalid,
inoperative, illegal or unenforceable to the extent that such other provisions
are not themselves actually in conflict with such constitution, statute or rule
of public policy, but this Agreement shall be reformed and construed in any such
jurisdiction or case as if such invalid, inoperative, illegal or unenforceable
provision had never been contained herein and such provision reformed so that it
would be valid, operative and enforceable to the maximum extent permitted in
such jurisdiction or in such case, except when such reformation and construction
could operate as an undue hardship on either party, or constitute a substantial
deviation from the general intent and purpose of such party as reflected in this
Agreement. The parties shall endeavor in good faith negotiations to replace the
invalid, inoperative, illegal or unenforceable provisions with valid, operative,
legal and enforceable provisions the economic effect of which comes as close as
possible to that of the invalid, inoperative, illegal or unenforceable
provisions.

     (g)  Counterparts. This Agreement may be executed in several counterparts,
each of which shall be deemed an original, but all of which together shall
constitute one and the same instrument, binding upon all the parties hereto. In
pleading or proving any provision of this Agreement, it shall not be necessary
to produce more than one of such counterparts.

     (h)  Section Headings. The headings contained in this Agreement are for
reference purposes only and shall not in any way affect the meaning or
interpretation of this Agreement.

     (i)  Governing Law. The validity, interpretation, construction and
performance of this Agreement shall be governed by the applicable laws of the
United States of America and the domestic substantive laws of the State of
Georgia without giving effect to any choice or conflict of laws provision or
rule that would cause the application of domestic substantive laws of any other
jurisdiction. Anything

                                       -6-

<PAGE>

in this Agreement to the contrary notwithstanding, in the event of any dispute
between the parties which results in a Legal Action, the prevailing party shall
be entitled to receive from the non-prevailing party reimbursement for
reasonable legal fees and expenses incurred by such prevailing party in such
Legal Action.

     (j)  Further Acts. Each party agrees that at any time, and from time to
time, before and after the consummation of the transactions contemplated by this
Agreement, it will do all such things and execute and deliver all such
agreements, assignments, instruments, other documents and assurances, as any
other party or its counsel reasonably deems necessary or desirable in order to
carry out the terms and conditions of this Agreement and the transactions
contemplated hereby or to facilitate the enjoyment of any of the rights created
hereby or to be created hereunder.

     (k)  Gender. Whenever used herein the singular number shall include the
plural, the plural shall include the singular, and the use of any gender shall
include all genders.

     (l)  Consultation with Counsel; No Representations. Gearon agrees and
acknowledges that he has had a full and complete opportunity to consult with
counsel of his own choosing concerning the terms, enforceability and
implications of this Agreement, and that ATC has made no representations or
warranties to him concerning the terms, enforceability or implications of this
Agreement other than as are reflected in this Agreement.

     IN WITNESS WHEREOF, the parties hereto have executed this Noncompetition
and Confidentiality Agreement, all pursuant to authority heretofore granted, as
of the date and year first above written.

                                        American Tower Corporation

                                        By: /s/ Steven B. Dodge
                                           -----------------------
                                           Name:
                                           Title:

                                            /s/ J. Michael Gearon, Jr.
                                           -------------------------------------
                                                J. Michael Gearon, Jr.

                                       -7-

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00036-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00036-of-00352.parquet"}]]