AMERICAN TOWER CORP /MA/
S-3, 2000-01-31
COMMUNICATIONS SERVICES, NEC
Previous: AMERICAN TOWER CORP /MA/, 8-K, 2000-01-31
Next: AMERICAN RESIDENTIAL EAGLE BOND TRUST 1999-2 COLLATERALIZED, 8-K, 2000-01-31



<PAGE>

    As filed with the Securities and Exchange Commission on January 31, 2000
                                                       Registration No. 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                  -----------
                                    FORM S-3
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                                  -----------
                           AMERICAN TOWER CORPORATION
             (Exact name of registrant as specified in its charter)
                Delaware                               65-0723837
     (State or Other Jurisdiction of    (I.R.S. Employer Identification Number)
     Incorporation or Organization)

               116 Huntington Avenue, Boston, Massachusetts 02116
  (Address, including zip code, and telephone number, including area code, of
                   registrant's principal executive offices)
                                  -----------
                                STEVEN B. DODGE
                           American Tower Corporation
                             116 Huntington Avenue
                          Boston, Massachusetts 02116
                                 (617) 375-7500
 (Name, address, including zip code, and telephone number, including area code,
                             of agent for service)
                                  -----------
                                    Copy to:
        NORMAN A. BIKALES, ESQ.                    JOHN T. BOSTELMAN
        Sullivan & Worcester LLP                  Sullivan & Cromwell
         One Post Office Square                     125 Broad Street
      Boston, Massachusetts 02109               New York, New York 10004

                                  -----------
   Approximate date of commencement of proposed sale to the public: As soon as
practicable after the effectiveness of this registration statement.
   If the only securities being registered on this form are being offered
pursuant to dividend or interest reinvestment plans, please check the box. [_]
   If any of the securities being registered on this form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or
interest reinvestment plans, check the following box. [_]
   If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following
box and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering. [_]
   If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [_]
   If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. [_]
                                  -----------
                        CALCULATION OF REGISTRATION FEE
<TABLE>
- ------------------------------------------------------------------------------
- ------------------------------------------------------------------------------
<CAPTION>
                                                       Proposed
                                         Proposed      Maximum
  Title of each Class of     Amount      Maximum      Aggregate    Amount of
     Securities to be        to be    Offering Price   Offering   Registration
      Registered(1)        Registered  Per Share(1)    Price(1)       Fee
- ------------------------------------------------------------------------------
<S>                        <C>        <C>            <C>          <C>
Class A Common Stock par
 value $.01 per share....  11,730,000     $38.38     $450,138,750   $118,837
- ------------------------------------------------------------------------------
- ------------------------------------------------------------------------------
</TABLE>

   (1) Estimated solely for the purpose of calculating the registration fee
pursuant to Rule 457 under the Securities Act of 1933.

   The Registrant hereby amends this Registration Statement on such date or
dates as may be necessary to delay its effective date until the Registrant
shall file a further amendment which specifically states that this Registration
Statement shall thereafter become effective in accordance with Section 8(a) of
the Securities Act of 1933 or until this Registration Statement shall become
effective on such date as the Commission, acting pursuant to said Section 8(a),
may determine.

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+The information in this prospectus is not complete and may be changed. We may +
+not sell these securities until the registration statement filed with the     +
+Securities and Exchange Commission is effective. This prospectus is not an    +
+offer to sell these securities and it is not soliciting an offer to buy these +
+securities in any state where the offer or sale is not permitted.             +
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                  SUBJECT TO COMPLETION DATED JANUARY 31, 2000

                                8,500,000 Shares

                              Class A Common Stock

                                   --------

  Our Class A common stock  is listed on the New  York Stock Exchange under  the
symbol "AMT". On January 27, 2000, the closing sale price of our Class A  common
stock was $38.38.

  The underwriters have an option to purchase a maximum of 1,275,000  additional
shares to cover over-allotments of shares.

  Holders of  Class A  common  stock are  entitled to  one  vote per  share  and
holders of Class B  common stock to  ten votes per  share generally. After  this
offering and the consummation of pending  acquisitions, Steven B. Dodge and  the
other executive officers  and directors,  together with  their affiliates,  will
have approximately 45.3% of the combined voting power.

  Investing in our Class A common stock involves risks. See "Risk Factors" on
page 10.

<TABLE>
<CAPTION>
                                                    Underwriting
                                          Price to  Discounts and  Proceeds to
                                           Public    Commissions  American Tower
                                          --------- ------------- --------------
<S>                                       <C>       <C>           <C>
Per Share................................   $           $              $
Total....................................   $           $             $
</TABLE>

  Delivery of the shares of Class A common stock will be made on or about     ,
2000.

  Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if
this prospectus is truthful or complete. Any representation to the contrary is
a criminal offense.

                           Credit Suisse First Boston


                The date of this prospectus is February  , 2000.
<PAGE>


                                     [LOGO]

                                     [map]

                                       i
<PAGE>

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

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                      Page
                                      ----
<S>                                   <C>
Note to Reader......................  (ii)
Summary.............................     1
Risk Factors........................    10
Capitalization......................    14
Use of Proceeds.....................    16
Dilution............................    16
Market Prices and Dividend Policy...    17
Unaudited Pro Forma Condensed
 Consolidated Financial Statements..    18
</TABLE>
<TABLE>
<CAPTION>
                                       Page
                                       ----
<S>                                    <C>
Description of Certain
 Indebtedness.......................    27
Description of Capital Stock........    29
Underwriting........................    32
Notice to Canadian Residents........    34
Validity of the Shares..............    35
Experts.............................    35
Where You Can Find More Information..   36
</TABLE>

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

   You should rely only on the information contained in this document or to
which we have referred you. We have not authorized anyone to provide you with
information that is different. This document may only be used where it is legal
to sell these securities. The information in this document may only be accurate
on the date of this document.

                                       i
<PAGE>

                                 NOTE TO READER

The Way We Describe Ourselves in this Prospectus

   We have been actively buying other companies and raising capital for our
business. We believe you will have a better picture of us if we show how we
look with all those transactions included. Therefore, we present a lot of the
information in this document on a "what if" basis to show how we would look if
we had owned these purchased companies for all of the various periods or now.
For the most part, this document describes us on this "what if" basis. This
"what if" information includes all significant businesses we have acquired
since the beginning of 1998. It also includes all significant businesses and
asset purchases that we are now in the process of acquiring, if we have signed
a legally binding contract.

   The special financial information called "pro forma" includes some but not
all of the "what if" acquisitions. This pro forma information includes only the
major acquisitions. We call the major acquisitions and transactions and other
"what if" information used in this pro forma information the "Pro Forma
Transactions". We occasionally refer to this pro forma information in the
document text, but label it clearly when we do that. Our historical financial
statements that we have incorporated by reference show us as we actually were,
without any "what if" changes.

   Finally, a few places in the text of this document also refer to us as we
actually exist, without any "what if" changes. We have tried to make it clear
when that is the case.

   Unless otherwise stated, all information contained in this document assumes
that we did not sell the additional shares the underwriters may buy at their
option to cover over-allotments. See "Underwriting" on page 32.

Defined Terms

   We use certain terms in this document repeatedly. They have a very specific
meaning that would be cumbersome to explain each time we use the term. For
example, it would be cumbersome to list all the transactions that comprise the
"Pro Forma Transactions" each time we use that term. Accordingly, we have given
that term a defined meaning, as indicated by the initial capitalized letters of
the term.

                                       ii
<PAGE>


                                    SUMMARY

   This summary highlights selected information about us, including our pending
mergers, acquisitions and other transactions. All information in this document
gives effect to pending transactions, unless the context otherwise indicates.
This summary is not complete and may not contain all of the information that
you should consider before investing in our shares. You should carefully read
this entire document, including the "Risk Factors" section beginning on page 10
and the financial statements, which are incorporated by reference from our 1998
Annual Report, March 1999 Quarterly Report, June 1999 Quarterly Report,
September 1999 Quarterly Report and the Current Report on Form 8-K, dated
September 17, 1999. We refer to those reports together as the "Historical
Financial Statements."

                                 AMERICAN TOWER

   We are a wireless communications and broadcast infrastructure company with
three operating segments.

  .  We operate a leading network of communications towers and are the
     largest independent operator of broadcast towers in the United States.

  .  We provide comprehensive network development services for wireless
     service providers and broadcasters.

  .  We operate a leading teleport business, which transmits video, voice,
     data and Internet communications worldwide.

   We estimate that our three operating segments accounted for the following
percentages of pro forma 1998 operating revenues:

  .  Towers--56%,

  .  Network development services--37%, and

  .  Teleports--7%.

   Towers. We believe we are the largest independent owner, operator and
developer of broadcast and wireless communications towers in North America.
Assuming consummation of all pending transactions, we operate a network of
approximately 10,400 multi-user sites in the United States and Mexico,
including approximately 300 broadcast tower sites. Of the 10,400 sites,
approximately 9,000 are owned or leased sites and approximately 1,400 are
managed or lease-sublease sites. Our U.S. network spans 48 states and the
District of Columbia, with tower clusters in 43 of the 50 largest U.S.
metropolitan statistical areas. Our developing Mexican network includes sites
in highly populated areas such as Mexico City, Monterrey, Guadalajara, and
Acapulco.

   Our primary business is the leasing of antenna space to a diverse range of
wireless communications and broadcast industries. Wireless industries served
include personal communications services ("PCS"), cellular, enhanced
specialized mobile radio ("ESMR"), specialized mobile radio ("SMR"), paging,
fixed microwave and fixed wireless. Our customers include AirTouch, Alltell,
AT&T, AT&T Wireless Services, Bell Atlantic Mobile, BellSouth, GTE Mobilnet,
Nextel, Omnipoint, PacBell, PageNet, PowerTel, PrimeCo PCS, Southwestern Bell
(SBC), Sprint PCS, Telligent, Western Wireless and WinStar. Through our
broadcast tower network we serve most major radio and television broadcasters,
including, ABC, AMFM, CBS, Clear Channel, Cox, Fox, Infinity, NBC, Paxson,
Paramount, Sinclair, Tribune, TV Azteca and Univision.

   Network Development Services. We are a leading provider of network
development services and components for both wireless service providers and
broadcasters. We offer full turnkey network development solutions to our
customers, consisting of RF engineering, network design, site acquisition,
zoning and other regulatory approvals, construction management, tower
construction and antenna installation. We also manufacture wireless
infrastructure components and fabricate steel used for broadcast towers and
other

                                       1
<PAGE>

structures. We provide site acquisition services to most of the major wireless
service providers and have constructed or are constructing towers on a build-
to-suit basis for wireless and broadcast companies such as AirTouch, AT&T
affiliates, AT&T Wireless Services, BellSouth, Nextel, Omnipoint, Paxson,
PrimeCo PCS, Sinclair and Southwestern Bell.

   We have performed network development services for other companies on more
than 10,000 sites. In 1998, we embarked on a major construction program with an
emphasis on build-to-suit projects. We constructed approximately 1,050 towers
for our own account in 1999, at an aggregate cost of approximately
$210.0 million, excluding broadcast towers. Our 2000 business plan calls for
construction of approximately 1,200 towers for our own account at an estimated
annual cost of between $196.0 million and $240.0 million. These figures do not
include the construction of broadcast towers.

   Teleports. We are a leading video, voice, data and Internet satellite
transmission company, providing services to both land and sea worldwide.
Assuming consummation of pending transactions, we own and operate more than 160
satellite antennas in various locations across the United States, with major
facilities in major metropolitan areas including New York, Washington D.C., San
Francisco and Dallas, as well as major facilities serving the Northeast,
Southwest, and Pacific Northwest. Our teleports are used by leading Internet,
voice and data providers as well as television networks, broadcasters and cable
programmers. Our customers include ABC, British Telecom, CBS, CNN, Deutsche
Telekom, Fox, MCI Worldcom, TCI, Telefonica and Uunet. Through our subsidiary,
Maritime Telecommunications Network, we are a leading provider of Internet,
voice and data services to major cruiselines.

   For the year ended December 31, 1998, we had pro forma net revenues of
$273.1 million and EBITDA of $91.9 million. For the nine months ended September
30, 1999, we had pro forma net revenues of $229.5 million and EBITDA of $83.3
million. This pro forma data includes the results of certain major acquisitions
and transactions, but not all of them.

   We believe that site leasing activities generate the highest profit margins.
We also believe that leasing activities are likely to grow rapidly because of
our recent and pending acquisitions and our build-to-suit and other
construction activities. These acquisitions and construction activities will
increase significantly the number of antenna sites available for leasing. The
industry trend towards outsourcing infrastructure needs may also result in a
decline in our site acquisition and construction activities for other
companies.

   We have a diversified base of more than 5,300 customers. Our largest
customer, AirTouch, accounted for approximately 25% of our pro forma annualized
August 1999 operating revenues. Our five largest customers accounted for
approximately 46% of those revenues. Annualized August 1999 revenues may not be
representative of historical revenues because revenues from service activities
are highly variable due to their transactional nature. For example, one
customer, Sprint PCS, accounted for approximately 12% of our pro forma
operating revenues for the nine months ended September 30, 1999, principally as
a result of several site acquisition projects during that period.

   We estimate that PCS accounted for more than 20% of our pro forma annualized
August 1999 operating revenues, cellular accounted for approximately 16% of
those revenues and paging accounted for approximately 12% of those revenues. We
believe that no other industry sector accounted for more than 10% of those
revenues. We believe, however, these industry sector percentages may not be
indicative of what we will experience in the future. The importance of the
different sectors will probably change because of the emergence of new wireless
data providers and the anticipated growth of PCS, cellular and ESMR, compared
to other wireless service providers. The relative contributions of the
different sectors will also be affected as major wireless service providers
create strategic alliances with independent operators, including in our case
AirTouch and AT&T. Finally, the percentage of operating revenues derived from
PCS will also be affected by the decline in our site acquisition and
construction activities for that sector, as providers continue to outsource
those requirements.

                                       2
<PAGE>


Growth Strategy

   We designed our growth strategy to create and then enhance our position as a
leader in each of our operating segments. Our goals were:

  .  to create a leading national footprint of desirable communications
     towers in all major markets in the United States,

  .  to establish the capacity to profitably serve most of the infrastructure
     needs of the wireless service and broadcast industries, and

  .  to create a leader in data networking through our teleport facilities.

   We implemented our strategy through a combination of acquisitions and
construction. Acquisitions were pursued initially with independent tower
operators and other consolidators and more recently with major wireless service
providers selling their towers. This acquisition strategy also broadened the
scope of our network development services.

   Our strategy has enabled us to create an organization with a depth of
personnel, computer and financial systems, sales and marketing, and engineering
and other technical expertise to take advantage of the growth in wireless
communications, digital television and the Internet. We believe we are well
positioned competitively for growth because we can meet the majority of
infrastructure requirements of wireless communications and digital television
and are playing an increasing role in addressing the Internet's infrastructure
needs. We will continue to pursue our growth strategy by:

  .  maximizing utilization of antenna sites through targeted sales and
     marketing techniques,

  .  capitalizing on our ability to provide full turnkey network development
     solutions principally through build-to-suit projects and other tower
     construction activities, and

  .  pursuing strategic mergers and acquisitions with independent tower
     operators and wireless service providers, designed principally (a) to
     achieve enhanced operating efficiencies, (b) to take advantage of
     divestiture opportunities presented by wireless service providers, (c)
     to broaden and strengthen our penetration of major markets, (d) to
     facilitate entry into new geographic markets in the U.S. and abroad, and
     (e) to complement our construction program.

Recent Developments

 Consummated Transactions

   Since January 1, 1999, we have consummated more than 60 transactions
involving the acquisition of more than 3,500 communications sites and related
businesses and three teleport businesses for an aggregate purchase price of
approximately $1.9 billion. This purchase price includes the payment of $1.2
billion in cash, the issuance of 21.2 million shares of Class A common stock,
and the assumption of $193.7 million of debt. The most recent principal
transactions were the following:

  Tower Transactions

   AirTouch transaction. In August 1999, we agreed to lease on a long-term
basis up to 2,100 towers from AirTouch Communications. These towers are located
in all of AirTouch's major markets, other than Los Angeles, San Diego and
Kansas City, including Albuquerque, Atlanta, Cleveland, Denver, Detroit,
Minneapolis, Omaha, Phoenix, Portland, San Francisco and Seattle. Our purchase
price, based on 2,100 towers, is $800.0 million in cash and a five-year warrant
to purchase 3.0 million shares of Class A common stock at $22.00 per share. The
first closing under this transaction occurred in January, 2000. At that
closing, we leased 800 towers, paid AirTouch $304.8 million in cash and issued
a warrant for 3.0 million shares. The remaining stages of the closing are
expected to occur, subject to the satisfaction of customary conditions, during
the first half of 2000.

                                       3
<PAGE>


   Under the lease, we are entitled to all income generated from leasing space
on the towers and are responsible for the payment of all expenses of the
towers, including ground rent. AirTouch has reserved space on the towers for
its antennas, for which it will pay us a site maintenance charge equal to
$1,500 per month for each non-microwave reserved space and $385 per month for
each microwave reserved space, with annual increases of 3%.

   We have also entered into an exclusive three-year build-to-suit agreement
with AirTouch. Under that agreement, we have the right to build all of
AirTouch's towers in all of the markets covered by the lease. AirTouch entered
into a separate master lease covering all towers to be constructed pursuant to
the build-to-suit agreement. Under the master lease, AirTouch will lease space
for a period of ten years and has the option to extend for five, five-year
periods. The rent is $1,500 per month for each non-microwave antenna site and
$385 per month for each microwave antenna site, with annual increases of 3%. We
expect this build-to-suit agreement will produce 400 to 500 towers.

   AT&T transaction. In September 1999, we agreed to purchase up to 1,942
towers from AT&T. These towers are located throughout the United States and
were constructed by AT&T for its microwave operations. The purchase price is
$260.0 million in cash, subject to adjustment if all towers are not purchased.
The first closing under this transaction occurred in January, 2000. At that
closing, we acquired 404 towers, entered into a build-to-suit agreement and
paid AT&T $134.1 million. The remaining stages of the closing are expected to
occur, subject to the satisfaction of customary conditions, during the first
half of 2000.

   AT&T entered into a master lease agreement covering those towers we acquired
and will acquire on which it conducts microwave operations. The lease has an
initial term of ten years and AT&T will have five, five-year renewal options.
The annual base rent for the microwave operations is approximately $1.0
million, payable in January of each lease year. The rent will be adjusted based
upon AT&T's use of the towers, except that any downward adjustment can be used
by AT&T as a credit only against future additional rent and not against the
base rent. AT&T currently uses 468 of these towers for its microwave
operations. We expect that as many as 50% of the towers may not be marketable,
at least in the near future, because of location.

   We also entered into a build-to-suit agreement with AT&T Wireless Services.
This agreement requires AT&T Wireless Services to present 1,200 sites
nationwide from which we will select and be required to build 1,000 towers.
There is a separate master lease with AT&T Wireless Services for the build-to-
suit towers. The initial term is ten years, and AT&T has three, five-year
renewals. The rent for lease supplements entered into in the initial year is
$1,350 per month, per antenna site, increasing annually by $50 per year for
lease supplements entered into in subsequent years. All rents will be subject
to a 4% increase per year.

   UNIsite merger. In January 2000, we merged with UNIsite. The purchase price
was $198.1 million, $149.4 million of which was paid in cash and $48.7 million
in assumption of UNIsite's debt. The purchase price is subject to adjustment
based on (a) the net working capital of UNIsite at closing and (b) the
estimated cost to complete certain of UNISite's towers. At closing, UNIsite had
more than 600 towers then completed or under construction. UNIsite's towers are
located primarily in the Northeast and Midwest.

   Galaxy merger. In January 2000, we merged with Galaxy Engineering Services,
a global turnkey provider of engineering consulting services, based in Atlanta,
GA. The aggregate purchase price paid to the other Galaxy stockholders
consisted of 523,113 shares of Class A common stock and $0.3 million in cash.
We had previously purchased one-third of Galaxy for $0.5 million and loaned the
$13.5 million. Galaxy provides wireless local loop/fixed wireless engineering,
radio frequency ("RF") network design, drive testing, optimization, competitive
benchmarking of wireless local loop, PCS and cellular networks, VQUAL(TM) voice
quality analysis and transport engineering, interconnect and microwave
services.

                                       4
<PAGE>


  Teleport Transactions

   ICG transaction. In December 1999, we acquired all of the stock of ICG
Satellite Services and its subsidiary, Maritime Telecommunications Network for
approximately $100.0 million in cash. The acquisition involved a major around-
the-clock teleport facility in New Jersey and a global maritime
telecommunications network headquartered in Miami, Florida. The acquired
company provides voice, data, Internet and compressed video satellite services
to major cruise lines, the U.S. military, Internet-related companies and
international telecommunications customers. The New Jersey teleport and
operations center has 12 existing antennas and one under construction that
access satellites covering the continental U.S., South America and the Atlantic
Ocean region.

 Pending Transactions

   We are a party to numerous pending transactions involving the acquisition of
more than 3,100 communications sites and related businesses and a major
teleport transaction for an aggregate purchase price of $816.8 million,
including the remaining portions of the AirTouch transaction and the AT&T
transaction. These transactions remain subject to regulatory approvals in
certain cases and other conditions. The principal transactions are the
following:

   TV Azteca transaction. In September 1999, we agreed to loan up to $120.0
million to TV Azteca, the owner of a major national television broadcast
network in Mexico, and to take over marketing responsibility for 200 of its
towers. The 20-year loan, which may be extended for an additional 50 years,
will bear net interest at approximately 11% per annum. We will be entitled to
receive 100% of the revenues generated by third party leases and will be
responsible for incremental operating expenses of third party tenants on the
towers during the term of the loan. In September 1999, we made an interim loan
of $60.0 million to TV Azteca when we entered into a letter of intent relating
to the loan and marketing agreements. The interim loan will mature on the
earlier of March 17, 2000 or the closing of the transaction. The closing is
subject to certain conditions, including the receipt of all necessary
regulatory approvals. Subject to satisfaction of those conditions the
transaction is scheduled to close in the first quarter of 2000.

   Iusacell transaction. In December 1999, we entered into a management
agreement for approximately 400 existing towers and a build-to-suit agreement
for approximately 200 towers with Grupo Iusacell, S.A. de C.V. and its
affiliates ("Iusacell"), the second largest wireless telecommunications
provider in Mexico. As part of the transaction, we have agreed to pay a $10.0
million refundable deposit upon the satisfaction of certain conditions to
retain the exclusive rights to acquire the approximately 400 existing towers
through 2005, or earlier at Iusacell's option, subject to certain restrictions.
The existing group of wireless towers that will be marketed under this
agreement and may be acquired, are located in urban and rural areas of Mexico
City, Guadalajara, Veracruz and Acapulco. The build-to-suit towers will be
constructed over the next two years in key metropolitan areas where Iusacell's
expansion plans are most critical.

   USEI transaction. In December 1999, we agreed to merge with U.S.
Electrodynamics. The purchase price of $60.0 million is payable through the
issuance of 1,040,153 shares of Class A common stock and cash. The purchase
price is subject to adjustment based on the net working capital and the long-
term debt of U.S. Electrodynamics at closing. The acquisition involves around-
the-clock teleport facilities in the Pacific Northwest, the Southwest and the
Northeast with a total of 52 antennas. The transaction is expected to close in
the second quarter of 2000, subject to satisfaction of customary conditions.

   Our principal executive offices are located at 116 Huntington Avenue,
Boston, Massachusetts 02116. Our telephone number is (617) 375-7500.

                                       5
<PAGE>

                                 THIS OFFERING

<TABLE>
<S>                                <C>
Class A common stock offered.....  8,500,000 shares

Common stock to be outstanding
 after this offering and the Pro
 Forma Transactions..............  153,465,623 shares of Class A common stock
                                     8,387,910 shares of Class B common stock
                                     2,422,804 shares of Class C common stock
                                   -----------
                                   164,276,337 shares of common stock
                                   ===========

Voting rights....................  The Class A common stock and the Class B common
                                   stock generally vote as a single class. Class A
                                   common stock has one vote per share and Class B
                                   common stock has ten votes per share. The Class A
                                   common stock, voting as a separate class, is
                                   entitled to elect two independent directors.
                                   Delaware corporate law and our charter also require
                                   class votes on some matters. Approximately 45.3% of
                                   the total voting power will be owned by Steven B.
                                   Dodge and other executive officers and directors,
                                   together with their affiliates, after this offering.
                                   The Class C common stock is generally nonvoting. We
                                   use the term "common stock" to mean all of these
                                   classes.

Other rights.....................  Each class of common stock has the same rights to
                                   dividends upon liquidation. The Class B common stock
                                   and the Class C common stock are convertible into
                                   Class A common stock on a share-for-share basis. The
                                   Class B common stock cannot be sold or transferred,
                                   except to certain categories of persons specified in
                                   our charter. The Class B common stock automatically
                                   converts into Class A common stock upon the
                                   occurrence of certain events.

New York Stock Exchange symbol
 (we refer to it as the "NYSE")..  AMT

Use of proceeds..................  We estimate the net proceeds from this offering,
                                   assuming a public offering price of $38.38 per share
                                   of Class A common stock, will be $313.5 million
                                   ($360.5 million if the underwriters' over-allotment
                                   option is exercised in full). We expect to use these
                                   proceeds to repay borrowings and, in the long term,
                                   to finance construction activities and pending and
                                   future mergers and acquisitions.
</TABLE>

                                       6
<PAGE>

                            SELECTED FINANCIAL DATA

   We have derived the following selected financial data from our historical
consolidated financial statements and our unaudited pro forma condensed
consolidated financial statements. The selected financial data should be read
in conjunction with the Historical Financial Statements. Prior to our
separation from our former parent on June 4, 1998, we operated as a subsidiary
of American Radio Systems and not as an independent company. Therefore, our
results of operations for periods prior to this may be different from what they
would have been had we operated as a separate, independent company.

   Year-to-year comparisons are significantly affected by our acquisitions and
construction of towers, both of which have been numerous during the periods
presented. Our principal acquisitions are described in "American Tower--Recent
Developments" under "Summary" on page 3 and in the notes to the Historical
Financial Statements.

   The pro forma balance sheet data gives effect, as of September 30, 1999, to
the pro forma transactions not then consummated: the AirTouch transaction, the
AT&T transaction, the UNIsite merger, the notes placement, and to this
offering. The pro forma statement of operations data and other operating data
gives effect to the pro forma transactions, as if each had occurred on January
1, 1998. We use the term pro forma transactions to mean certain of our major
acquisitions and financings as follows: the OmniAmerica merger, the TeleCom
merger, the separation from American Radio Systems, the ATC merger, the Wauka
transaction, the UNIsite merger, the AirTouch transaction, the AT&T
transaction, our public offerings in July 1998 and February 1999 and our
private placements in February and October 1999. Pro forma transactions do not
include all of the consummated or pending acquisitions or pending construction.
See "American Tower--Recent Developments" under "Summary" on page 3 and
"Unaudited Pro Forma Condensed Consolidated Financial Statements" on page 18.

   We account for all of the included acquisitions as purchases. This means
that for accounting and financial reporting purposes, we include the results of
operations and assets of the acquired companies with ours only after the
closing of the acquisition. The pro forma financial data reflects certain
adjustments, as explained elsewhere in this document. Therefore, any comparison
of the pro forma financial data with the historical financial data for periods
before 1998 is inappropriate. See "Unaudited Pro Forma Condensed Consolidated
Financial Statements" on page 18.

   We use the term "tower cash flow" to mean operating income (loss) before
depreciation and amortization, tower separation expenses and corporate general
and administrative expenses. We use the term "tower separation expenses" to
refer to the one-time expenses incurred as a result of our separation from
American Radio Systems. We use "EBITDA" to mean operating income (loss) before
depreciation and amortization and tower separation expenses. "After-tax cash
flow" means income (loss) before extraordinary losses, plus depreciation and
amortization. We do not consider tower cash flow, EBITDA and after-tax cash
flow as a substitute for alternative measures of operating results or cash flow
from operating activities or as a measure of our profitability or liquidity.
These measures of performance are not calculated in accordance with generally
accepted accounting principles. However, we have included them because they are
generally used in the communications site industry as a measure of a company's
operating performance. More specifically, we believe they can assist in
comparing company performances on a consistent basis without regard to
depreciation and amortization. Our concern is that depreciation and
amortization can vary significantly among companies depending on accounting
methods, particularly where acquisitions are involved, or on non-operating
factors including historical cost bases. We believe tower cash flow is useful
because it enables you to compare tower performances before the effect of tower
separation and corporate general and administrative expenses that do not relate
directly to performance.

                                       7
<PAGE>

                           AMERICAN TOWER CORPORATION

                           Selected Financial Data(1)

<TABLE>
<CAPTION>
                          July 17, 1995
                           (inception)     Year Ended            Year Ended          Nine Months Ended
                             through      December 31,        December 31, 1998      September 30, 1999
                          December 31,  ------------------  ----------------------  ---------------------
                              1995       1996      1997     Historical  Pro Forma   Historical  Pro Forma
                          ------------- -------  ---------  ----------  ----------  ----------  ---------
                                            (in thousands, except per share data)
Statements of Operations
Data:
<S>                       <C>           <C>      <C>        <C>         <C>         <C>         <C>
Operating revenues......     $   163    $ 2,897  $  17,508  $ 103,544   $  273,092  $ 169,100   $229,512
                             -------    -------  ---------  ---------   ----------  ---------   --------
Operating expenses:
 Operating expenses
  excluding
  depreciation and
  amortization, tower
  separation, and
  corporate general and
  administrative
  expenses..............          60      1,362      8,713     61,751      172,624     99,525    137,227
 Depreciation and
  amortization..........          57        990      6,326     52,064      212,859     92,919    168,955
 Tower separation
  expense...............                                       12,772       12,772
 Corporate general and
  administrative
  expense...............         230        830      1,536      5,099        8,599      6,395      9,020
                             -------    -------  ---------  ---------   ----------  ---------   --------
   Total operating
    expenses............         347      3,182     16,575    131,686      406,854    198,839    315,202
                             -------    -------  ---------  ---------   ----------  ---------   --------
(Loss) income from
 operations.............        (184)      (285)       933    (28,142)    (133,762)   (29,739)   (85,690)
Interest expense........                            (3,040)   (23,229)     (89,745)   (17,497)   (63,073)
Interest income and
 other, net.............                     36        251      9,217        9,217     13,899     13,899
Minority interest in net
 earnings of
 subsidiaries(2)........                   (185)      (193)      (287)        (287)       (79)       (79)
                             -------    -------  ---------  ---------   ----------  ---------   --------
Loss before income taxes
 and extraordinary
 losses.................        (184)      (434)    (2,049)   (42,441)    (214,577)   (33,416)  (134,943)
Benefit (provision) for
 income taxes...........          74        (45)       473      4,491       60,060        942     36,650
                             -------    -------  ---------  ---------   ----------  ---------   --------
Loss before
 extraordinary losses...     $  (110)   $  (479) $  (1,576) $ (37,950)  $ (154,517) $ (32,474)  $(98,293)
                             =======    =======  =========  =========   ==========  =========   ========
Basic and diluted loss
 per common share before
 extraordinary
 losses(3)..............     $ (0.00)   $ (0.01) $   (0.03) $   (0.48)  $    (0.95) $   (0.22)  $  (0.60)
                             =======    =======  =========  =========   ==========  =========   ========
Basic and diluted
 weighted average common
 shares outstanding(3)..      48,732     48,732     48,732     79,786      163,158    147,588    164,098
                             =======    =======  =========  =========   ==========  =========   ========
Other Operating Data:
Tower cash flow.........     $   103    $ 1,535  $   8,795  $  41,793   $  100,468  $  69,575   $ 92,285
EBITDA..................        (127)       705      7,259     36,694       91,869     63,180     83,265
EBITDA margin...........        (N/A)      24.3%      41.5%      35.4%        33.6%      37.4%      36.3%
After-tax cash flow.....         (53)       511      4,750     14,114       58,342     60,445     70,662
Cash (used for) provided
 by operating
 activities.............         (51)     2,230      9,913     18,429          --      56,561        --
Cash used for investing
 activities.............         --         --    (216,783)  (350,377)         --    (736,763)       --
Cash provided by
 financing activities...          63        132    209,092    513,527          --     535,738        --
</TABLE>

<TABLE>
<CAPTION>
                                                             Nine Months Ended
                                             December 31,    September 30, 1999
                                             -------------- --------------------
                                             1997    1998   Historical Pro Forma
                                             ------ ------- ---------- ---------
Tower Data:
<S>                                          <C>    <C>     <C>        <C>
Towers operated at end of period(4).........   674    2,492   4,607      9,736
Towers constructed(5).......................    84      503     695        N/A
</TABLE>

                                       8
<PAGE>

<TABLE>
<CAPTION>
                                Year Ended December 31,
                                      Historical                 September 30, 1999
                          ------------------------------------- --------------------
                          1995(1)   1996     1997       1998    Historical Pro Forma
                          -------  ------- --------  ---------- ---------- ---------
                                               (in thousands)
Balance Sheet Data:
<S>                       <C>      <C>     <C>       <C>        <C>        <C>
Cash and cash
 equivalents............  $   12   $ 2,373 $  4,596  $  186,175 $   41,711 $  55,451
Working capital
 (deficiency), excluding
 current portion of
 long-term debt.........     (40)      663   (2,208)     93,602     44,633    51,498
Property and equipment,
 net....................   3,759    19,710  117,618     449,476    892,245   892,245
Unallocated purchase
 price..................     --        --       --          --         --  1,356,061
Total assets............   3,863    37,118  255,357   1,502,343  2,620,558 3,887,033
Long-term debt,
 including current
 portion................     --      4,535   90,176     281,129    378,640 1,226,849
Total stockholders'
 equity.................   3,769    29,728  153,208   1,091,746  2,157,734 2,516,689
</TABLE>
- --------------------
(1) We were organized on July 17, 1995.
(2) Represents the minority interest in net earnings of our non-wholly-owned
    subsidiaries.
(3) Basic and diluted loss per common share before extraordinary losses has
    been computed using (a) in the case of historical information, for periods
    prior to June 4, 1998, the number of shares outstanding following the
    separation from American Radio Systems and (b) in the case of pro forma
    information, the number of shares expected to be outstanding following the
    Pro Forma Transactions and this offering.
(4) Includes information with respect to our company only and assumes
    consummation of all pending transactions, including those not included in
    the Pro Forma Transactions. Does not include towers under construction. See
    Note (5) below.
(5) Includes towers constructed in each period by us, including towers
    constructed for and owned by third parties. These numbers do not include
    towers constructed by companies we acquired during the applicable period.

                                       9
<PAGE>

                                  RISK FACTORS

   You should consider carefully the following factors and other information in
this document before deciding to invest in our securities.

If we cannot keep raising capital, our growth will be impeded

   Without additional capital, we would need to curtail our acquisition and
construction programs. We expect to use borrowed funds for most of this
capital. However, we must continue to satisfy financial ratios and to comply
with financial and other covenants in order to do so. If our revenues and cash
flow do not meet expectations, we may lose our ability to borrow money. These
same factors, as well as market conditions beyond our control, could make it
difficult or impossible for us to sell stock as an alternative to borrowing.

Meeting payments on our large debt could be a burden to us

   Our high debt level makes us vulnerable to downturns in our operations. This
high debt level requires us to use most of our cash flow to make interest and
principal payments. If we do not generate sufficient cash flow through our
operations to make interest and principal payments, we may be forced to sell
debt or equity securities or to sell some of our core assets. This could be
harmful to our business and to our securityholders. Market conditions or our
own financial situation may require us to make these sales on unattractive
terms.

Demand for tower space may be beyond our control

   Many of the factors affecting the demand for tower space, and therefore our
cash flow, are beyond our control. Those factors include:

  .  consumer demand for wireless services,

  .  the financial condition of wireless service providers and their
     preference for owning or leasing antenna sites,

  .  the growth rate of wireless communications or of a particular wireless
     segment,

  .  the number of wireless service providers in a particular segment,
     nationally or locally,

  .  governmental licensing of broadcast rights,

  .  zoning, environmental and other government regulations, and

  .  technological changes.

   "Roaming" and "resale" arrangements could also adversely affect demand.
These arrangements enable a wireless service provider to serve customers
outside its license area through agreements with other providers. Wireless
service providers might consider roaming and resale arrangements preferable to
leasing antenna space from us.

New tower construction, particularly build-to-suit projects, involves
uncontrollable risks and increasing competition

   Our increasing focus on major build-to-suit projects for wireless service
providers entails several unique risks. The first is the greater dependence on
a single customer. Second, because of intense competition for these projects,
we may grant the wireless service provider non-economic lease and control
provisions more favorable than our general terms. Finally, although we have the
benefit of an "anchor" tenant in build-to-suit projects, we may not be able to
find a sufficient number of additional tenants. In fact, one reason wireless
service providers may want build-to-suit arrangements is to share or escape the
costs of an undesirable site. A site may be undesirable because it has high
construction costs or may be considered a poor location by other providers.

                                       10
<PAGE>

   Our expanded construction activities also involve other substantial risks.
These risks include:

  .  increasing our debt and the amount of payments on that debt,

  .  uncontrollable risks that could delay or increase the cost of a project,

  .  increasing competition for construction sites and experienced tower
     construction companies, resulting in significantly higher costs and
     failure to meet time schedules,

  .  failing to meet time schedules could result in our paying significant
     penalties to prospective tenants, particularly in build-to-suit
     situations, and

  .  possible lack of sufficient experienced personnel to manage an expanded
     construction program.

   We cannot control the main factors that can prevent, delay or increase the
cost of construction. These factors include:

  .  zoning and local permitting requirements,

  .  environmental group opposition,

  .  availability of skilled construction personnel and construction
     equipment,

  .  adverse weather conditions, and

  .  federal regulations.

Our acquisition strategy involves increasing acquisition costs, high debt
levels and potential management and integration issues

   Increased competition, which we believe will continue, has resulted in
substantially higher acquisition costs, particularly for towers being sold by
wireless service providers. These prices, in turn, result in high debt and debt
service requirements. Equally important, the increased size of our acquisitions
from wireless service providers could create certain problems we have not faced
in the past:

  .  dependence on a limited number of customers,

  .  lease and control provisions more favorable to the wireless service
     provider than those we give our tenants generally,

  .  integration of major national networks into our operational systems,

  .  demands on managerial personnel that could divert their attention from
     other aspects of our business, and

  .  potential antitrust constraints, either in local markets or on a
     regional or national basis, that could impede future acquisitions or
     require selective divestitures at unfavorable prices.

   An additional risk is the acquisition of significant numbers of towers that
may have limited marketing potential. See "American Tower--Recent
Developments--Consummated Transactions--Tower Transactions--AT&T transaction"
under "Summary" on page 4.

Covenants in our credit facilities could impede our growth strategy

   Our growth strategy may be impaired by restrictive covenants in our credit
facilities. The most significant of these covenants impose limits on our
aggregate borrowings and require us to meet certain financial ratios and comply
with all of the financial and other covenants in order to borrow funds. Events
beyond our control may affect our ability to meet these requirements. If these
covenants restrict our ability to borrow funds, our acquisition strategy and
construction program will be harmed. Also, certain types of acquisitions and
investments in other companies are limited in accordance with a formula based,
in part, on proceeds of equity offerings.

                                       11
<PAGE>

We are dependent on key personnel and would be adversely affected if they leave

   The loss of our Chief Executive Officer, Steven B. Dodge, and other
executive officers has a greater likelihood of having a material adverse effect
upon us than it would on most other companies of our size. Our growth strategy
is highly dependent on the efforts of Mr. Dodge and our other executive
officers. Our ability to raise capital is dependent in part on the reputation
of Mr. Dodge. You should be aware that we have not entered into employment
agreements with Mr. Dodge or most of our other executive officers. We may not
be able to retain our executive officers, including those with employment
agreements, or other key personnel or prevent them from competing with us if
they leave.

Increasing foreign operations could create certain operational and financial
risks

   Our recent expansion into Mexico, and other possible foreign operations in
the future, could result in adverse financial consequences and operational
problems not experienced in the United States. We have committed to make a
substantial loan to a Mexican company and to construct a sizable number of
towers in that country. Among the risks of foreign operations are governmental
expropriation and regulation, inability to repatriate earnings or other funds,
currency fluctuations, difficulty in recruiting trained personnel, and language
and cultural differences that could impair management control and operations.

New technologies could make our tower antenna leasing services less desirable
to potential tenants

   Mobile satellite systems and other new technologies could compete with land-
based wireless communications systems, thereby reducing the demand for tower
lease space and other services we provide. The FCC has granted license
applications for several low-earth orbiting satellite systems that are intended
to provide mobile voice or data services. In addition, the emergence of new
technologies could reduce the need for tower-based transmission and reception
and have an adverse affect on our operations.

   The growth in delivery of video services by direct broadcast satellites and
the development and implementation of signal combining technologies, which
permit one antenna to service two different transmission frequencies and,
therefore, two customers, could also reduce the demand for our tower space by
wireless service providers.

We could be harmed if perceived health risks from radio emissions are
substantiated

   If a connection between radio emissions and possible negative health
effects, including cancer, were established, we would be materially and
adversely affected. The results of several substantial studies by the
scientific community in recent years have been inconclusive. We and the lessees
of antenna sites on our towers are subject to government regulations relating
to radio frequency emissions. We do not maintain any significant insurance with
respect to these matters.

Pro forma financial information is based on estimates and assumptions and may
not be indicative of actual future results

   Our actual future results could vary materially and adversely from those
reflected in the pro forma financial information we have included in this
document. That information is based upon a number of assumptions we believe to
be reasonable. However, our two most significant acquisitions, the AirTouch and
AT&T transactions, do not involve the acquisition of businesses. The towers
involved in those acquisitions were operated as part of the wireless service
businesses of AirTouch and AT&T. Separate financial records were not maintained
and financial statements were never prepared for the operation of those towers.
We have, however, compiled certain revenue and expense data of those towers in
the pro forma information. In the case of certain expenses, we have estimated
amounts based on our own experience with comparable towers. Neither our
auditors, AirTouch's auditors, AT&T's auditors nor the underwriters have
expressed any opinion or provided any form of assurance with respect to
AirTouch or AT&T's historical data presented in the unaudited pro forma
financial information.

                                       12
<PAGE>

We could have liability under environmental laws

   Under various federal, state and local environmental laws, we, as an owner,
lessee or operator of real estate, may be liable for the substantive costs of
remediating soil and groundwater contaminated by hazardous wastes. Some of
these laws may impose responsibility and liability on us even if we did not
cause the contamination or even know about it. Almost all of the towers we own
and operate, other than rooftop towers, are located on parcels of land, which
could result in substantial environmental liability. Our liability often will
continue even if we sell or cease to lease the property.

Control by our principal stockholders could deter mergers where you could get
more than current market price for your stock

   Control by Mr. Dodge and others may have the effect of discouraging a merger
or other takeover of our company in which holders of Class A common stock may
be paid a premium for their shares over then-current market prices. Mr. Dodge,
together with a limited number of our directors, may be able to control or
block the vote on mergers and other matters submitted to the common
stockholders. On January 1, 2000, after giving effect to this offering, our
directors and executive officers, together with their affiliates, owned
"beneficially" approximately 45.3% of the voting power of the common stock. Mr.
Dodge, together with his affiliates, so owned "beneficially" approximately
29.0% of the combined voting power.

Our common stock does not pay dividends; you will experience immediate and
substantial dilution upon investment

   We have never paid a dividend on our common stock and do not expect to pay
cash dividends in the foreseeable future. Rather, we intend to retain any
available earnings for the growth of our business. In addition, our credit
facilities effectively restrict the payment of cash dividends or other
distributions and the repurchase, redemption or other acquisition of our equity
securities. At September 30, 1999, our net tangible book value was a deficit of
$2.75 per share. If you purchase shares in this offering, you will sustain
immediate and substantial dilution of approximately $39.08 per share.

Our forward-looking statements could prove to be wrong and we might suffer a
material adverse effect

   Our forward-looking statements are subject to risks and uncertainties. You
should note that many factors, some of which are discussed in this section or
elsewhere in this prospectus or in the documents we have incorporated by
reference, could affect our company in the future and could cause our results
to differ materially from those expressed in our forward-looking statements.
Forward-looking statements include those regarding our goals, beliefs, plans or
current expectations and other statements regarding matters that are not
historical facts. For example, when we use the words "believe," "expect,"
"anticipate" or similar expressions, we are making forward-looking statements.
Forward-looking statements include statements concerning:

  .  the outcome of our growth strategy,

  .  future results of operations,

  .  liquidity and capital expenditures,

  .  construction and acquisition activities,

  .  debt levels and the ability to obtain financing and make payments on our
     debt,

  .  regulatory developments and competitive conditions in the communications
     site and wireless carrier industries,

  .  projected growth of the wireless communications and wireless carrier
     industries, and

  .  general economic conditions.

   We are not required to release publicly the results of any revisions to
these forward-looking statements we may make to reflect future events or
circumstances.


                                       13
<PAGE>

                                 CAPITALIZATION

   The first column in the following table shows our actual historical
capitalization as of September 30, 1999. The second column shows our
capitalization as adjusted on a "what if" basis to show the effect of the Pro
Forma Transactions, as if we had completed them on September 30, 1999. The
third column shows our capitalization as further adjusted to show the effect of
this offering, as if we had completed it on September 30, 1999.

   Management believes that the assumptions used provide a reasonable basis on
which to present such pro forma capitalization. You should read the
capitalization table below in conjunction with our historical financial
statements which are incorporated by reference and the "Unaudited Pro Forma
Condensed Consolidated Financial Statements" on page 18. We have provided the
capitalization table below for informational purposes only. It is not
necessarily indicative of our capitalization or financial condition had we
consummated the transactions and events referred to above on the date assumed.
It is also not necessarily indicative of our future capitalization or financial
condition.

<TABLE>
<CAPTION>
                                          September 30, 1999 (in thousands)
                                          -----------------------------------
                                                       Pro Forma
                                                          for      Pro Forma
                                                       Pro Forma    for this
                                          Historical  Transactions  Offering
                                          ----------  ------------ ----------
<S>                                       <C>         <C>          <C>
Cash and cash equivalents................ $   41,711   $   55,451  $   55,451
                                          ==========   ==========  ==========
Long-term debt, including current
 portion(1)(2):
  Borrowings under the credit
   facilities............................ $  368,000   $  876,200  $  562,745
  Convertible notes......................                 600,000     600,000
  Other long-term debt...................     10,640       64,104      64,104
                                          ----------   ----------  ----------
    Total long-term debt.................    378,640    1,540,304   1,226,849
                                          ----------   ----------  ----------
Stockholders' equity(3):
Common Stock(4)
  Class A common stock...................      1,445        1,445       1,530
  Class B common stock...................         88           88          88
  Class C common stock...................         24           24          24
Additional paid-in capital...............  2,239,881    2,285,381   2,598,751
Accumulated deficit......................    (82,176)     (82,176)    (82,176)
Treasury stock...........................     (1,528)      (1,528)     (1,528)
                                          ----------   ----------  ----------
    Total stockholders' equity...........  2,157,734    2,203,234   2,516,689
                                          ----------   ----------  ----------
    Total capitalization................. $2,536,374   $3,743,538  $3,743,538
                                          ==========   ==========  ==========
</TABLE>

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

(1) For additional information, see "Unaudited Pro Forma Condensed Consolidated
    Financial Statements" on page 18 and "Management's Discussion and Analysis
    of Financial Condition and Results of Operations--Liquidity and Capital
    Resources" in the September 1999 Quarterly Report.
(2) See "Description of Certain Indebtedness" on page 27 for additional
    information regarding the components and terms of our long-term debt.
(3) Consists of (a) preferred stock, par value $.01 per share, 20,000,000
    authorized shares, none issued or outstanding: (b) Class A common stock,
    par value $.01 per share, 500,000,000 authorized shares; shares issued and
    outstanding: 144,466,550 (historical and pro forma for the Pro Forma
    Transactions), 152,966,550 (pro forma for this offering); (c) Class B
    common stock, par value $.01 per share, 50,000,000 authorized shares;
    shares issued and outstanding; 8,811,940 (historical, pro forma for the Pro
    Forma Transactions and pro forma for this offering); and (d) Class C common
    stock, par value $.01 per share,

                                       14
<PAGE>

   10,000,000 authorized shares; shares issued and outstanding; 2,422,804
   (historical, pro forma for the Pro Forma Transactions and pro forma for
   this offering). Outstanding share numbers do not give effect to subsequent
   conversions of shares of Class B common stock or Class C common stock to
   Class A common stock.
(4) The number of outstanding shares does not include: (a) shares of Class A
    common stock issuable upon conversion of Class B common stock or Class C
    common stock, (b) shares issuable upon exercise of options currently
    outstanding to purchase an aggregate of 14,285,184 shares of common stock,
    (c) shares issuable pursuant to pending mergers and acquisitions (other
    than those included in Pro Forma Transactions), or (d) shares issuable
    upon exercise of warrants to purchase an aggregate of 3.0 million shares
    of Class A common stock issued in the AirTouch transaction.


                                      15
<PAGE>

                                USE OF PROCEEDS

   We estimate that our net proceeds from this offering (after we deduct the
underwriting discount and estimated offering expenses) will be $313.5 million
($360.5 million if the underwriters' over-allotment option is exercised in
full). We expect to use these net proceeds, in the short term, to repay bank
borrowings. In the long-term, those net proceeds, together with bank
borrowings, will be used to finance the construction of towers, our remaining
obligations with respect to acquisitions, and for general working capital
purposes. We may also utilize these net proceeds, together with bank borrowings
to finance, among other things, acquisitions of additional communications sites
or other related businesses.

   As of January 31, 2000, on a pro forma basis, assuming consummation of the
Pro Forma Transactions and all other pending acquisitions, but not this
offering, we would have had indebtedness under our credit facilities of
approximately $1.5 billion. After giving effect to this offering and assuming
the use of the net proceeds described above, as of such date, on such pro forma
basis, we would have had borrowings under our credit facilities of $1.2
billion. The Chase Manhattan Bank ("Chase") is a lender under our credit
facilities and will receive its 4.9% proportionate share of any repayments of
borrowings. Chase is an affiliate of Chase Equity Associates, which together
with its affiliates owns approximately 4.0% of our common stock and has a
representative on our board of directors.

                                    DILUTION

   As of September 30, 1999, our pro forma net tangible book value, after
giving effect to the Pro Forma Transactions, was a deficit of $428.6 million or
($2.75) per share of common stock. "Pro Forma net tangible book value per
share" represents the amount of total pro forma assets, less pro forma
intangible assets and unallocated purchase price, reduced by the amount of
total pro forma liabilities and divided by the pro forma number of shares of
common stock outstanding. After giving effect to the application of the net
proceeds from the sale of shares in this offering (after deduction of the
underwriting discount and estimated offering expenses), our as adjusted pro
forma net tangible book value as of such date would have been a deficit of
$115.2 million or ($0.70) per share. This represents an immediate increase to
existing stockholders in such pro forma negative net tangible book value of
$2.05 and an immediate decrease in net tangible book value to investors
purchasing shares in this offering of $39.08 per share.

   The following table illustrates the dilution per share as described above:

<TABLE>
      <S>                                                      <C>     <C>
      Assumed initial public offering price per share................   $38.38
        Pro forma net tangible book value (deficit) per share
         before this offering................................. $(2.75)
        Increase attributable to this offering................   2.05
                                                               ------
      As adjusted pro forma net tangible book value (deficit) per
       share after this offering.....................................     (.70)
                                                                       -------
      Dilution to new investors......................................   $39.08
                                                                       =======
</TABLE>

                                       16
<PAGE>

                       MARKET PRICES AND DIVIDEND POLICY

Market Price Data

   On February 27, 1998, our Class A common stock commenced trading on a "when-
issued" basis on the inter-dealer bulletin board of the over-the-counter
market. Our Class A common stock commenced trading on the NYSE on June 5, 1998
(the day after we separated from American Radio Systems). The following table
presents reported high and low sale prices of our Class A common stock in the
over-the-counter market or on the Composite Tape of the NYSE.

<TABLE>
<CAPTION>
                                1998                            High     Low
                                ----                           ------- -------
      <S>                                                      <C>     <C>
      Quarter Ended March 31 (commencing February 27, 1998)... $20.250 $15.500
        Quarter Ended June 30.................................  26.125  18.750
        Quarter Ended September 30............................  28.625  14.375
        Quarter Ended December 31.............................  29.625  13.250

<CAPTION>
                                1999
                                ----
      <S>                                                      <C>     <C>
        Quarter Ended March 31................................  30.250  20.500
        Quarter Ended June 30.................................  26.875  20.500
        Quarter Ended September 30............................  26.000  19.500
        Quarter Ended December 31.............................  33.250  17.125

<CAPTION>
                                2000
                                ----
      <S>                                                      <C>     <C>
        Quarter Ended March 31 (through January 28)...........  44.625  28.562
</TABLE>

   The outstanding shares of common stock and number of registered holders as
of December 31, 1999 were as follows:

<TABLE>
<CAPTION>
                                                              Class
                                                 -------------------------------
                                                      A          B         C
                                                 ----------- --------- ---------
      <S>                                        <C>         <C>       <C>
      Outstanding shares........................ 144,965,623 8,387,910 2,422,804
      Registered holders........................         570        61         1
</TABLE>

Dividends

   We have never paid a dividend on any class of common stock. We anticipate
that we will retain future earnings, if any, to fund the development and growth
of our business. We do not anticipate paying cash dividends on shares of common
stock in the foreseeable future. Our credit facilities restrict the payment of
cash dividends by our subsidiaries. See "Description of Capital Stock--Dividend
Restrictions" on page 31.

                                       17
<PAGE>

        UNAUDITED PRO FORMA CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

   We have included our unaudited pro forma condensed consolidated balance
sheet as of September 30, 1999 and our unaudited pro forma condensed
consolidated statements of operations for the year ended December 31, 1998 and
for the nine months ended September 30, 1999. To the extent required, these pro
forma statements have been adjusted for:

  .  the OmniAmerica merger, the TeleCom merger, the separation from American
     Radio Systems, the ATC merger, the Wauka transaction, the UNIsite
     merger, the AirTouch transaction and the AT&T transaction,

  .  our public offerings of Class A common stock in July 1998 and February
     1999 and our private placement in February 1999,

  .  the notes placement in October 1999, and

  .  this offering.

   The pro forma financial statements do not reflect all of our consummated or
pending acquisitions. The adjustments assume that all pro forma transactions
were consummated on January 1, 1998, in the case of the unaudited pro forma
condensed consolidated statement of operations. The adjustments assume that the
pending pro forma transactions were consummated as of September 30, 1999 in the
case of the unaudited pro forma condensed consolidated balance sheet. You
should read the pro forma financial statements in conjunction with the
Historical Financial Statements. Although the AirTouch transaction and the AT&T
transaction do not involve the acquisition of a business, we have provided pro
forma information related to these transactions, as we believe such information
is material to your investment decision.

   The pro forma financial statements may not reflect our financial condition
or our results of operations had these events actually occurred on the date
specified. They may also not reflect our financial condition or our results of
operations of operating as a separate, independent company during the periods.
Finally, they may not reflect our future financial condition or results of
operations.

   We use the term "Pro Forma Transactions" to include all of the transactions
referred to above, other than this offering. See "American Tower--Recent
Developments--Consummated Transactions" under "Summary" on page 3 for a
description of certain of the Pro Forma Transactions and Historical Financial
Statements for a description of the other Pro Forma Transactions.

                                       18
<PAGE>

                           AMERICAN TOWER CORPORATION

            UNAUDITED PRO FORMA CONDENSED CONSOLIDATED BALANCE SHEET

                               SEPTEMBER 30, 1999
                                 (in thousands)

<TABLE>
<CAPTION>
                                       Adjustments     Pro Forma   Adjustments Pro Forma
                                      for Pro Forma  for Pro Forma  for This    for This
                          Historical Transactions(a) Transactions  Offering(b)  Offering
                          ---------- --------------- ------------- ----------- ----------
<S>                       <C>        <C>             <C>           <C>         <C>
         ASSETS
Cash and cash equiva-
 lents..................  $   41,711   $   13,740     $   55,451               $   55,451
Accounts receivable,
 net....................      38,818        1,806         40,624                   40,624
Other current assets....      39,010        6,868         45,878                   45,878
Notes receivable........      72,156      (25,000)        47,156                   47,156
Property and equipment,
 net....................     892,245                     892,245                  892,245
Unallocated purchase
 price..................                1,356,061      1,356,061                1,356,061
Intangible assets, net..   1,275,807                   1,275,807                1,275,807
Deferred tax asset......     113,003                     113,003                  113,003
Deposits and other as-
 sets...................     147,808      (87,000)        60,808                   60,808
                          ----------   ----------     ----------               ----------
  Total.................  $2,620,558   $1,266,475     $3,887,033               $3,887,033
                          ==========   ==========     ==========               ==========
       LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities,
 excluding current
 portion of long-term
 debt...................  $   74,906   $   15,549     $   90,455               $   90,455
Deferred income taxes...                   42,268         42,268                   42,268
Other long-term liabili-
 ties...................       3,369        1,494          4,863                    4,863
Long-term debt,
 including current
 portion................     378,640      561,664        940,304    $(313,455)    626,849
Convertible notes, net
 of discount............                  600,000        600,000                  600,000
Minority interest.......       5,909                       5,909                    5,909
Stockholders' equity....   2,157,734       45,500      2,203,234      313,455   2,516,689
                          ----------   ----------     ----------    ---------  ----------
  Total.................  $2,620,558   $1,266,475     $3,887,033    $     --   $3,887,033
                          ==========   ==========     ==========    =========  ==========
</TABLE>


 See Notes to Unaudited Pro Forma Condensed Consolidated Financial Statements.

                                       19
<PAGE>

                          NOTES TO UNAUDITED PRO FORMA

                  CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

   We have prepared the unaudited pro forma condensed consolidated balance
sheet as of September 30, 1999 to give effect, as of such date, to the AirTouch
transaction, the AT&T transaction, the UNIsite merger and the notes placement
in October, 1999, the only Pro Forma Transactions not completed by that date.
We will account for all of the Pro Forma Transactions under the purchase method
of accounting.

(a) The following table sets forth the pro forma balance sheet adjustments as
of September 30, 1999 (in thousands).

<TABLE>
<CAPTION>
                                                                           Total
                                                                        Adjustments
                                                                            for
                          AirTouch        AT&T     UNIsite     Notes     Pro Forma
                         Transaction   Transaction  Merger   Placement  Transactions
                         -----------   ----------- --------  ---------  ------------
<S>                      <C>           <C>         <C>       <C>        <C>
         ASSETS
Cash and cash
 equivalents............                           $ 13,740              $   13,740
Accounts receivable,
 net....................                              1,806                   1,806
Other current assets....                              6,868                   6,868
Notes receivable........                            (25,000)                (25,000)
Unallocated purchase
 price(1)...............  $845,500      $ 265,000   245,561               1,356,061
Deposits and other
 assets.................  (100,000)        (3,000)           $  16,000      (87,000)
                          --------      ---------  --------  ---------   ----------
  Total.................  $745,500      $ 262,000  $242,975  $  16,000   $1,266,475
                          ========      =========  ========  =========   ==========
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities,
 excluding current
 portion of long-term
 debt...................                $   5,000  $ 10,549              $   15,549
Deferred income taxes...                             42,268                  42,268
Other long-term
 liabilities............                              1,494                   1,494
Long-term debt,
 including current
 portion................  $700,000        257,000   188,664  $(584,000)     561,664
Convertible notes, net
 of discount............                                       600,000      600,000
Stockholders' equity....    45,500(2)                                        45,500
                          --------      ---------  --------  ---------   ----------
  Total.................  $745,500      $ 262,000  $242,975  $  16,000   $1,266,475
                          ========      =========  ========  =========   ==========
</TABLE>

   The following table sets forth the purchase prices and related pro forma
financing of the transactions described above (in millions).

<TABLE>
<CAPTION>
                                                                   Fair Value of
                                         Purchase Price Borrowings Debt Assumed
                                         -------------- ---------- -------------
<S>                                      <C>            <C>        <C>
AirTouch transaction....................    $ 845.5(2)   $ 700.0
AT&T transaction........................      260.0        257.0
UNIsite merger..........................      165.0        135.2      $ 53.4
</TABLE>
- ---------------------
(1) Upon completion of our evaluation of the purchase price allocations, we
    expect that the average life of the assets should approximate 15 years.
(2) We have issued warrants having a fair value of approximately $45.5 million
    to purchase an aggregate of 3.0 million shares of Class A common stock at
    $22.00 per share.

(b) To record the issuance of 8.5 million shares of Class A common stock based
on the initial public offering price of $38.375 per share and the net proceeds
(estimated at approximately $313.5 million) of this offering.

                                       20
<PAGE>

                           AMERICAN TOWER CORPORATION

       UNAUDITED PRO FORMA CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS

                          Year Ended December 31, 1998
                     (in thousands, except per share data)

<TABLE>
<CAPTION>
                                      Adjustments for   Pro Forma   Adjustments
                                         Pro Forma    for Pro Forma  for this          Pro Forma
                          Historical  Transactions(a) Transactions   Offering      for this Offering
                          ----------  --------------- ------------- -----------    -----------------
<S>                       <C>         <C>             <C>           <C>            <C>
Operating revenues......  $ 103,544      $ 169,548      $ 273,092                      $ 273,092
Operating expenses
 excluding depreciation
 and amortization, tower
 separation, and
 corporate general and
 administrative expenses
 .......................     61,751        110,873        172,624                        172,624
Depreciation and amorti-
 zation.................     52,064        160,795        212,859                        212,859
Tower separation ex-
 pense..................     12,772                        12,772                         12,772
Corporate general and
 administrative
 expense................      5,099          3,500          8,599                          8,599
                          ---------      ---------      ---------                      ---------
Loss from operations....    (28,142)      (105,620)      (133,762)                      (133,762)
                          ---------      ---------      ---------                      ---------
Other (income) expense:
  Interest expense......     23,229         91,592        114,821    $(25,076)(b)         89,745
  Interest income and
   other, net...........     (9,217)                       (9,217)                        (9,217)
  Minority interest in
   net earnings of
   subsidiaries.........        287                           287                            287
                          ---------      ---------      ---------    --------          ---------
Total other (income) ex-
 pense..................     14,299         91,592        105,891     (25,076)            80,815
                          ---------      ---------      ---------    --------          ---------
Income (loss) before
 income taxes and
 extraordinary losses...    (42,441)      (197,212)      (239,653)     25,076           (214,577)
Provision (benefit) for
 income taxes(c)........     (4,491)       (65,600)       (70,091)     10,031            (60,060)
                          ---------      ---------      ---------    --------          ---------
(Loss) income before ex-
 traordinary losses.....  $ (37,950)     $(131,612)     $(169,562)   $ 15,045          $(154,517)
                          =========      =========      =========    ========          =========
Basic and diluted net
 loss per common share
 before extraordinary
 losses.................  $   (0.48)           N/A      $   (1.10)        N/A          $   (0.95)
                          =========      =========      =========    ========          =========
Basic and diluted common
 shares outstanding(d)..     79,786         74,872        154,658       8,500            163,158
                          =========      =========      =========    ========          =========
</TABLE>


 See Notes to Unaudited Pro Forma Condensed Consolidated Financial Statements.

                                       21
<PAGE>

                          NOTES TO UNAUDITED PRO FORMA

            CONDENSED CONSOLIDATED FINANCIAL STATEMENTS--(Continued)


   The unaudited pro forma condensed consolidated statement of operations for
the year ended December 31, 1998 gives effect to the Pro Forma Transactions, as
if each of them had occurred on January 1, 1998.

   (a) To record the results of operations for the Pro Forma Transactions. We
have adjusted the results of operations to: (1) reverse historical interest
expense; and (2) record an increase of net interest expense of $91.6 million
for the year ended December 31, 1998 as a result of the increased debt after
giving effect to the July 1998 and February 1999 equity financings and the
notes placement.

   We have also adjusted the results of operations to reverse historical
depreciation and amortization expense of $20.3 million for the year ended
December 31, 1998 and record depreciation and amortization expense of $160.8
million for the year ended December 31, 1998 based on estimated allocations of
purchase prices. With respect to unallocated purchase price, we have determined
pro forma depreciation and amortization expense based on an expected average
life of 15 years. Debt discount is being amortized using the effective interest
method. Debt issuance costs are being amortized on a straight line basis over
the term of the obligations. Amortization of debt discount and issuance costs
are included within interest expense.

   We have not carried forward corporate general and administrative expenses of
the prior owners into the pro forma condensed consolidated financial
statements. These costs represent duplicative facilities and compensation to
owners and/or executives we did not retain, including charges related to the
accelerated vesting of stock options and bonuses that were directly
attributable to the purchase transactions. Because we already maintain our own
separate corporate headquarters, which provides services substantially similar
to those represented by these costs, we do not expect them to recur following
the acquisition. After giving effect to an estimated $3.5 million of
incremental costs, we believe that we have existing management capacity
sufficient to provide the services without incurring additional incremental
costs.

   The following table sets forth the historical results of operations for the
Pro Forma Transactions for the year ended December 31, 1998 (in thousands).

<TABLE>
<CAPTION>
                            Wauka      ATC     Separation   July    OmniAmerica TeleCom   February
                         Transaction  Merger    From ARS  Offering    Merger     Merger   Offerings
                         ----------- --------  ---------- --------  ----------- --------  ---------
<S>                      <C>         <C>       <C>        <C>       <C>         <C>       <C>
Operating revenues......  $  4,736   $ 11,337                        $ 82,313   $ 12,273
Operating expenses
 excluding depreciation
 and amortization, and
 corporate general and
 administrative
 expenses...............     2,065      3,936                          73,461      2,701
Depreciation and
 amortization...........       986      3,125                           8,325      5,990
Corporate general and
 administrative
 expense................     3,520                                                13,932
                          --------   --------                        --------   --------
(Loss) income from
 operations.............    (1,835)     4,276                             527    (10,350)
Other (income) expense:
 Interest expense.......       997      3,333   $  8,901  $(15,736)     2,638      2,873  $(19,184)
 Interest income........                                                            (660)
 Other, net.............         9      5,144                            (458)       843
                          --------   --------   --------  --------   --------   --------  --------
(Loss) income before
 income taxes...........  $ (2,841)  $ (4,201)  $ (8,901) $ 15,736   $ (1,653)  $(13,406) $ 19,184
                          ========   ========   ========  ========   ========   ========  ========
</TABLE>


                                       22
<PAGE>

                          NOTES TO UNAUDITED PRO FORMA

            CONDENSED CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

<TABLE>
<CAPTION>
                                                                                        Total
                                                                                     Adjustments
                                                                                       for Pro
                         UNIsite    AirTouch        AT&T         Notes    Pro Forma     Forma
                          Merger   Transaction   Transaction   Placement Adjustments Transactions
                         --------  -----------   -----------   --------- ----------- ------------
<S>                      <C>       <C>           <C>           <C>       <C>         <C>
Operating revenues...... $  4,414   $  51,566(e)  $   2,909(f)                        $ 169,548
Operating expenses
 excluding depreciation
 and amortization, and
 corporate general and
 administrative
 expenses...............    1,615      19,400(g)      7,695(g)                          110,873
Depreciation and
 Amortization...........    1,870                                         $ 140,499     160,795
Corporate general and
 administrative
 expense................   12,273                                           (26,225)      3,500
                         --------   ---------     ---------     -------   ---------   ---------
(Loss) income from
 operations.............  (11,344)     32,166        (4,786)               (114,274)   (105,620)
Other (income) expense:
 Interest expense.......    6,320      64,000        20,800     $(7,403)     24,053      91,592
 Interest income........   (2,331)                                            2,991
 Other, net.............      (27)                                           (5,511)
                         --------   ---------     ---------     -------   ---------   ---------
(Loss) income before
 income taxes........... $(15,306)  $ (31,834)    $ (25,586)    $ 7,403   $(135,807)  $(197,212)
                         ========   =========     =========     =======   =========   =========
</TABLE>

(b) To record a reduction in interest expense as a result of the use of
proceeds from this offering. For purposes of the adjustment we have used an
interest rate of 8%.

(c) To record the tax effect of the pro forma adjustments and impact on our
estimated effective tax rate. The actual effective tax rate may be different
once we determine the final purchase price allocations.

(d) Includes shares of Class A common stock issued pursuant to: the Wauka
transaction--1.4 million, the ATC merger--28.8 million, the OmniAmerica
merger--16.8 million, the TeleCom merger--3.9 million, July offering--27.9
million, the February offerings--26.2 million, and this offering--8.5 million.

(e) Includes additional revenues to be recognized in connection with the
AirTouch lease agreement, assuming all 2,100 towers are subleased.
Approximately $3.5 million of existing third-party lease revenues has not been
included.

(f) Includes additional revenues to be recognized in connection with the AT&T
and AT&T Wireless Services lease agreements, assuming the acquisition of all
1,942 towers. Approximately $8.8 million of existing third-party lease revenues
has not been included.

(g) The towers involved in each of these acquisitions were operated as part of
the wireless service businesses of AirTouch and AT&T. Accordingly, separate
financial records were not maintained and financial statements were never
prepared for the operation of these towers. In addition to land leases that we
will assume, we have estimated certain operating expenses we would expect to
incur based on our own experience with comparable towers. Such estimates
include expenses related to utilities, repairs and maintenance, insurance and
real estate taxes. These operating expenses are based on management's best
estimate and, as such, the actual expenses may be different than the estimate
presented.

                                       23
<PAGE>

                           AMERICAN TOWER CORPORATION

       UNAUDITED PRO FORMA CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS

                      Nine Months Ended September 30, 1999
                     (in thousands, except per share data)

<TABLE>
<CAPTION>
                                     Adjustments for   Pro Forma   Adjustments    Pro Forma
                                        Pro Forma    for Pro Forma  for this      for this
                          Historical Transactions(a) Transactions   Offering      Offering
                          ---------- --------------- ------------- -----------    ---------
<S>                       <C>        <C>             <C>           <C>            <C>
Operating revenues......   $169,100     $  60,412      $ 229,512                  $ 229,512
Operating expenses
 excluding depreciation
 and amortization and
 corporate, general and
 administrative
 expenses...............     99,525        37,702        137,227                    137,227
Depreciation and amorti-
 zation.................     92,919        76,036        168,955                    168,955
Corporate general and
 administrative
 expense................      6,395         2,625          9,020                      9,020
                           --------     ---------      ---------                  ---------
Loss from operations....    (29,739)      (55,951)       (85,690)                   (85,690)
Other (income) expense:
  Interest expense......     17,497        64,332         81,829    $(18,756)(b)     63,073
  Interest income and
   other, net...........    (13,899)                     (13,899)                   (13,899)
  Minority interest in
   net earnings
   of subsidiaries......         79                           79                         79
                           --------     ---------      ---------    --------      ---------
Total other (income) ex-
 pense..................      3,677        64,332         68,009     (18,756)        49,253
Income (Loss) before in-
 come taxes.............    (33,416)     (120,283)      (153,699)     18,756       (134,943)
Provision (Benefit) for
 income taxes(c)........       (942)      (43,210)       (44,152)      7,502        (36,650)
                           --------     ---------      ---------    --------      ---------
Net Income (Loss).......   $(32,474)    $ (77,073)     $(109,547)   $ 11,254      $ (98,293)
                           ========     =========      =========    ========      =========
Basic and diluted net
 loss per common share
 before extraordinary
 losses.................   $  (0.22)    $     N/A      $   (0.70)        N/A      $   (0.60)
                           ========     =========      =========    ========      =========
Basic and diluted common
 shares outstanding(d)..    147,588         8,010        155,598       8,500        164,098
                           ========     =========      =========    ========      =========
</TABLE>



 See Notes to Unaudited Pro Forma Condensed Consolidated Financial Statements.

                                       24
<PAGE>

                          NOTES TO UNAUDITED PRO FORMA

            CONDENSED CONSOLIDATED FINANCIAL STATEMENTS--(Continued)


   The unaudited pro forma condensed consolidated statement of operations for
the nine months ended September 30, 1999 gives effect to the pro forma
transactions not consummated as of January 1, 1999, which includes the Omni
merger, the Telecom merger, the UNIsite merger, the AirTouch transaction, the
AT&T transaction, the February offerings, the notes placement and this
offering. We will account for all of the Pro Forma Transactions under the
purchase method of accounting. See "American Tower--Recent Developments--
Consummated Transactions" under "Summary" on page 3 for a description of
certain of the pending Pro Forma Transactions and the Historical Financial
Statements for a description of the other pro forma transactions.

   (a) To record the results of operations for the pro forma transactions. We
have adjusted the results of operations to: (1) reverse historical interest
expense; and (2) record an increase in net interest expense of $64.3 million
for the nine months ended September 30, 1999 as a result of the increased debt
after giving effect to the proceeds of the February 1999 equity financings and
the notes placement.

   We have also adjusted the results of operations to reverse historical
depreciation and amortization expense of $6.6 million for the nine months ended
September 30, 1999 and recorded depreciation and amortization expense of $76.0
million for the nine months ended September 30, 1999 based on estimated
allocations of purchase prices. With respect to unallocated purchase price, we
have determined pro forma depreciation and amortization expense based on an
expected average life of 15 years. Debt discount is being amortized using the
effective interest method. Debt issuance costs are being amortized on a
straight-line basis over the term of the obligation. Amortization of debt
discount and issuance costs are included within interest expense.

   We have not carried forward corporate general and administrative expenses of
the prior owners into the pro forma condensed consolidated financial
statements. These costs represent duplicative facilities and compensation to
owners and/or executives we did not retain, including charges related to the
accelerated vesting of stock options and bonuses that were directly
attributable to the purchase transactions. Because we already maintain our own
separate corporate headquarters, which provides services substantially similar
to those represented by these costs, we do not expect them to recur following
the acquisition. After giving effect to an estimated $2.6 million of
incremental costs, we believe that we have existing management capacity
sufficient to provide the services without incurring additional incremental
costs.

   The following table sets forth the historical results of operations for the
pro forma transactions for the nine months ended September 30, 1999 (in
thousands).

<TABLE>
<CAPTION>
                                                                                                                  Total
                                                                                                               Adjustments
                                                                                                                 for Pro
                     OmniAmerica TeleCom   February  UNIsite    AirTouch       AT&T        Notes    Pro Forma     Forma
                       Merger     Merger   Offerings  Merger   Transaction  Transaction  Placement Adjustments Transactions
                     ----------- --------  --------- --------  -----------  -----------  --------- ----------- ------------
<S>                  <C>         <C>       <C>       <C>       <C>          <C>          <C>       <C>         <C>
Operating
 revenues..........    $12,246   $  2,029            $  5,183    $38,675(e)   $ 2,279(f)                        $  60,412
Operating expenses
 excluding
 depreciation and
 amortization, and
 corporate general
 and administrative
 expenses..........     12,257        549               4,575     14,550(g)     5,771(g)                           37,702
Depreciation and
 amortization......      2,372      1,201               3,005                                       $  69,458      76,036
Corporate general
 and administrative
 expense...........      2,882     10,173               6,906                                         (17,336)      2,625
                       -------   --------   -------  --------    -------      -------     -------   ---------   ---------
(Loss) income from
 operations........     (5,265)    (9,894)             (9,303)    24,125       (3,492)                (52,122)    (55,951)
Other (income)
 expense:
 Interest expense,
  net..............        746        521   $(1,499)    5,702                             $(5,534)     64,396      64,332
 Interest income...        (14)                          (681)                                            695
 Other, net........        816       (106)                511                                          (1,221)
                       -------   --------   -------  --------    -------      -------     -------   ---------   ---------
(Loss) income
 before income
 taxes.............    $(6,813)  $(10,309)  $ 1,499  $(14,835)   $24,125      $(3,492)    $ 5,534   $(115,992)  $(120,283)
                       =======   ========   =======  ========    =======      =======     =======   =========   =========
</TABLE>

                                       25
<PAGE>

                          NOTES TO UNAUDITED PRO FORMA

            CONDENSED CONSOLIDATED FINANCIAL STATEMENTS--(Continued)


(b) To record a reduction in interest expense as a result of the use of
proceeds from this offering. For purposes of this adjustment we have used an
interest rate of 8%.

(c) To record the tax effect of the pro forma adjustments and impact on our
estimated effective tax rate. The actual effective tax rate may be different
once we determine the final purchase price allocations.

(d) Includes shares of Class A common stock issued pursuant to: the OmniAmerica
merger--16.8 million, the TeleCom merger--3.9 million, the February offerings--
26.2 million, and this offering--8.5 million.

(e) Includes additional revenues to be recognized in connection with the
AirTouch lease agreement, assuming all 2,100 towers are leased. Approximately
$2.6 million of existing third-party lease revenues has not been included.

(f) Includes additional revenues to be recognized in connection with the AT&T
and AT&T Wireless Services lease agreements, assuming acquisition of all 1,942
towers. Approximately $6.6 million of existing third-party lease revenues has
not been included.

(g) The towers involved in each of these acquisitions were operated as part of
the wireless service businesses of AirTouch and AT&T. Accordingly, separate
financial records were not maintained and financial statements were never
prepared for the operation of these towers. In addition to land leases that we
will assume, we have estimated certain operating expenses we would expect to
incur based on our own experience with comparable towers. Such estimates
include expenses related to utilities, repairs and maintenance, insurance and
real estate taxes. These operating expenses are based on management's best
estimate and, as such, the actual expenses may be different than the estimate
presented.

                                       26
<PAGE>

                      DESCRIPTION OF CERTAIN INDEBTEDNESS

Credit Facilities

   The description below summarizes the more important terms of our bank
borrowing arrangements, which we refer to as the "credit facilities." We have
filed copies of the loan agreement with the banks and the SEC as an exhibit to
our Current Report on Form 8-K dated January 28, 2000 which we have
incorporated by reference. You should refer to that agreement for the complete
terms of the credit facilities. The capitalized words used in the description
below have specialized meanings defined in that agreement.

   Several of our principal operating subsidiaries (we refer to them
collectively as the "borrower subsidiaries") have borrowed and expect to
continue to borrow under the credit facilities. The credit facilities provide
for up to $2.0 billion of loans to us, the funding of which has been committed
to by the banks. The credit facilities also contemplate possible additional
borrowings of up to $500.0 million, although the banks are not committed to
fund those borrowings. Borrowings under the credit facilities are also limited
by the amount of cash flow and value of the assets of the borrower subsidiaries
and the Restricted Subsidiaries.

   The credit facility is made up of three separate types of loans:

     (a) a $650.0 million reducing revolving credit facility maturing on June
  30, 2007,

     (b) a $850.0 million multiple-draw term loan maturing on June 30, 2007,
  and

     (c) a $500.0 million term loan maturing on December 31, 2007.

   The borrower subsidiaries are required to reduce the revolving credit
commitments and to amortize the term loans quarterly, commencing March 31,
2003, in increasing amounts designed to repay the loans by maturity. We are
also required to repay the loans, and reduce the revolving credit commitments,
out of the proceeds of asset sales and sales of equity or debt securities, by
us or our subsidiaries, and out of cash flow. We can repay the loans
voluntarily at any time, without penalty. As of January 31, 2000, the $500.0
million term loan, $230.0 million of the multiple draw term loans and $75.0
million of the reducing revolving loan were outstanding.

   We may incur indebtedness under the credit facilities for acquisitions,
construction and other capital expenditures, working capital and general
corporate purposes.

   The credit facilities require the maintenance of the following ratios:

     (a) Total Debt to Annualized Operating Cash Flow of not more than 7.75:1
  declining in stages to 4.00:1 by January 1, 2004 and thereafter;

     (b) Annualized Operating Cash Flow to Interest Expense of not less than
  1.25:1 increasing in stages to 3.00:1 by January 1, 2004 and thereafter;

     (c) Annualized Operating Cash Flow to Pro Forma Debt Service of not less
  than 1.10:1; and

     (d) Annualized Operating Cash Flow to Fixed Charges of not less than
  1.00:1.

   The credit facilities contain certain financial and operational covenants
and other restrictions with which the borrower subsidiaries and the Restricted
Subsidiaries must comply, whether or not there are any borrowings outstanding.
These include restrictions on certain types of acquisitions, not including
towers and communications sites, indebtedness, liens, capital expenditures,
investments in Unrestricted Subsidiaries, and the ability of the borrower
subsidiaries and the Restricted Subsidiaries to pay dividends or make other
distributions.

   We and the Restricted Subsidiaries have guaranteed all of the loans. We have
secured the loans by liens on substantially all assets of the borrower
subsidiaries and the Restricted Subsidiaries and all outstanding capital stock
and other debt and equity interests of all of our direct and indirect
subsidiaries.

                                       27
<PAGE>

Convertible Notes

   In October 1999, we issued 6.25% Convertible Notes Due 2009 in an aggregate
principal amount of $300.0 million and of 2.25% Convertible Notes Due 2009 at
an issue price of $300.1 million, representing 70.52% of their principal amount
at maturity of $425.5 million. The difference between the issue price and the
principal amount at maturity of the 2.25% Notes will be accreted each year as
interest expense in our financial statements. The 6.25% notes are convertible
into shares of Class A common stock at a conversion price of $24.40 per share.
The 2.25% notes are convertible into shares of Class A common stock at a
conversion price of $24.00 per share.

   We may not redeem the 6.25% notes prior to October 22, 2002. Thereafter, we
can redeem those notes, at our option, in whole or in part at a redemption
price initially of 103.125% of the principal amount. The redemption price
declines ratably immediately after October 15 of each following year to 100% of
the principal amount in 2005. We may not redeem the 2.25% notes prior to
October 22, 2003. Thereafter, we can redeem those notes, at our option, in
whole or in part at increasing redemption prices designed to reflect the
accrued original issue discount. We are also required to pay accrued and unpaid
interest in all redemptions of notes.

   Holders may require us to repurchase all or any of their 6.25% notes on
October 22, 2006 at their principal amount, together with accrued and unpaid
interest. Holders may require us to repurchase all or any of their 2.25% notes
on October 22, 2003 at $802.93, which is its issue price plus accreted original
issue discount, together with accrued and unpaid interest. We may, at our
option, elect to pay the repurchase price of each series in cash or shares of
Class A common stock, or any combination thereof. Our credit facilities require
us to pay entirely in stock unless we obtain bank consent.

   The indentures under which the notes are outstanding do not contain any
restrictions on the payment of dividends, the incurrence of debt or liens or
the repurchase of our equity securities or any financial covenants.

                                       28
<PAGE>

                          DESCRIPTION OF CAPITAL STOCK

   The description below summarizes the more important terms of our capital
stock. Because this section is a summary, it does not describe every aspect of
the capital stock. This summary is subject to and qualified in its entirety by
reference to the provisions of our restated certificate of incorporation, as
amended. We refer to it as the "restated certificate." A copy of the restated
certificate has been filed as an exhibit to the quarterly report on Form 10-Q
dated August 16, 1999, which we have incorporated by reference. Wherever
particular defined terms or provisions of the restated certificate are referred
to, those terms and provisions are incorporated by reference as a part of the
statements made, and the statements are qualified in their entirety by that
reference.

General

   Our authorized capital stock consists of 20,000,000 shares of preferred
stock, $.01 par value per share, 500,000,000 shares of Class A common stock,
$.01 par value per share, 50,000,000 shares of Class B common stock, $.01 par
value per share, and 10,000,000 shares of Class C common stock, $.01 par value
per share. The number of outstanding shares of common stock as of December 31,
1999 is shown on page 17.

Preferred Stock

   General. Our board of directors will determine the designations,
preferences, limitations and relative rights of the 20,000,000 authorized and
unissued shares of preferred stock, including:

  .  the distinctive designation of each series and the number of shares that
     will constitute the series,

  .  the voting rights, if any, of shares of the series,

  .  the dividend rate on the shares of the series, any restriction,
     limitation or condition upon the payment of the dividends, whether
     dividends will be cumulative, and the dates on which dividends are
     payable,

  .  the prices at which, and the terms and conditions on which, the shares
     of the series may be redeemed, if the shares are redeemable,

  .  the purchase or sinking fund provisions, if any, for the purchase or
     redemption of shares of the series,

  .  any preferential amount payable upon shares of the series upon our
     liquidation or the distribution of our assets,

  .  the price or rates of conversion at which, and the terms and conditions
     on which the shares of the series may be converted into other
     securities, if the shares are convertible, and

  .  whether the series can be exchanged, at our option, into debt
     securities, and the terms and conditions of any permitted exchange.

   The issuance of preferred stock, or the issuance of rights to purchase
preferred stock, could discourage an unsolicited acquisition proposal.

Common Stock

   Dividends. Holders of record of shares of common stock on the record date
fixed by our board of directors are entitled to receive dividends as declared
by our board of directors out of funds legally available for the purpose. No
dividends may be declared or paid in cash or property on any share of any class
of common stock, however, unless simultaneously the same dividend is declared
or paid on each share of the other classes of common stock. Dividends in the
form of shares of stock of any company, including our company or any of our
subsidiaries, are excepted from that requirement. In that case, the shares may
differ as to voting rights to the extent that voting rights now differ among
the different classes of common stock. In the case of any dividend payable in
shares of common stock, holders of each class of common stock are entitled to
receive the same percentage dividend, payable in shares of that class, as the
holders of each other class. Dividends and other distributions on common stock
are also subject to the rights of holders of any series of preferred stock or
debt that may be outstanding from time to time. See "--Dividend Restrictions"
on page 31.

                                       29
<PAGE>

   Voting Rights. Holders of shares of Class A common stock and Class B common
stock have the exclusive voting rights and will vote as a single class on all
matters submitted to a vote of the stockholders. The foregoing is subject to
the requirements of Delaware corporate law, special provisions governing
election of directors and the rights of holders of any series of preferred
stock that may be outstanding from time to time. Each share of Class A common
stock is entitled to one vote and each share of Class B common stock is
entitled to ten votes. The holders of the Class A common stock, voting as a
separate class, have the right to elect two independent directors. The Class C
common stock is nonvoting except as otherwise required by Delaware corporate
law.

   Delaware corporate law requires the affirmative vote of the holders of a
majority of the outstanding shares of any class or series of common stock to
approve, among other things, a change in the designations, preferences and
limitations of the shares of that class or series. The restated certificate,
however, requires the affirmative vote of the holders of not less than 66 2/3%
of the Class A common stock and Class B common stock, voting as a single class,
to amend most of the provisions of the restated certificate, including those
relating to the provisions of the various classes of common stock,
indemnification of directors, exoneration of directors for certain acts and the
super-majority provision.

   The restated certificate:

  .  limits the aggregate voting power of Steven B. Dodge and his controlled
     entities to 49.99% of the aggregate voting power of all shares of
     capital stock entitled to vote generally for the election of directors,
     less the voting power represented by the shares of Class B common stock
     acquired by Thomas H. Stoner, a director, and purchasers affiliated with
     him in the January 1998 private offering and owned by them or any of
     their controlled entities or family members at the applicable time,

  .  prohibits future issuances of Class B common stock, except upon exercise
     of then outstanding options and pursuant to stock dividends or stock
     splits,

  .  limits transfers of Class B common stock to permitted transferees,

  .  provides for automatic conversion of the Class B common stock to Class A
     common stock if the aggregate voting power of Mr. Dodge, Mr. Stoner and
     their respective controlled entities fall below either (a) 50% of Mr.
     Dodge's initial aggregate voting power on June 8, 1998 which was
     approximately 42.6%; or (b) 20% of the aggregate voting power of all
     shares of common stock at the time outstanding, and

  .  requires the holders of a majority of Class A common stock to approve
     amendments adversely affecting the Class A common stock.

   On January 1, 2000, after giving effect to this offering, our directors and
executive officers, together with their affiliates, owned beneficially
approximately 45.3% of the combined voting power of our common stock. On that
date, after giving effect to this offering, Mr. Dodge, together with his
affiliates, owned beneficially approximately 29.0% of the combined voting
power.

   Conversion Provisions.  Shares of Class B common stock and Class C common
stock are convertible, at any time at the option of the holder, on a share for
share basis into shares of Class A common stock. The present owner of Class C
common stock can convert that stock only upon the occurrence of a conversion
event or with the consent of our board of directors. Shares of Class B common
stock automatically convert into shares of Class A common stock upon any sale,
transfer, assignment or other disposition other than (a) to permitted
transferees, or (b) pursuant to pledges but not to the pledgee upon
foreclosure. Permitted transferees includes certain family members and other
holders of Class B common stock.

   Liquidation Rights. Upon our liquidation, dissolution or winding up the
holders of each class of common stock are entitled to share ratably in all
assets available for distribution after payment in full of creditors and
payment in full to holders of preferred stock then outstanding of any amount
required to be paid to them.

   Other Provisions. The holders of common stock are not entitled to preemptive
or subscription rights. The shares of common stock presently outstanding are
validly issued, fully paid and nonassessable.

                                       30
<PAGE>

   In any merger, consolidation or business combination, the holders of each
class of common stock must receive the identical consideration to that received
by holders of each other class of common stock, except if shares of common
stock or common stock of any other company are distributed, the shares may
differ as to voting rights to the same extent that voting rights then differ
among the different classes of common stock.

   No class of common stock may be subdivided, consolidated, reclassified or
otherwise changed unless, concurrently, the other classes of common stock are
subdivided, consolidated, reclassified or otherwise changed in the same
proportion and in the same manner.

Dividend Restrictions

   Our borrower subsidiaries are prohibited under the terms of their credit
facilities from paying cash dividends or making other distributions on, or
making redemptions, purchases or other acquisitions of, their capital stock or
other equity interests, including preferred stock, except that, beginning on
April 15, 2004, if no default exists or would be created thereby under the
credit facilities, our borrower subsidiaries may pay cash dividends or make
other distributions to the extent that restricted payments, as defined in the
credit facilities, do not exceed 50% of excess cash flow, as defined in the
credit facilities, for the preceding calendar year.

Delaware Business Combination Provisions

   Under Delaware corporate law, certain "business combinations," including the
issuance of equity securities, between a Delaware corporation and any
"interested stockholder" must be approved by the holders of at least 66 2/3% of
the voting stock not owned by the interested stockholder if it occurs within
three years of the date the person became an interested stockholder. The voting
requirement does not apply, however, if, before the acquisition, the
corporation's board of directors approved either the business combination or
the transaction which resulted in the person becoming an interested
stockholder. "Interested stockholder" means any person who owns, directly or
indirectly, 15% or more of the voting power of the corporation's shares of
capital stock. The provision does not apply to Mr. Dodge because our board of
directors approved the transaction pursuant to which he became an interested
stockholder.

Listing of Class A Common Stock

   Our Class A common stock is traded on the NYSE under the symbol "AMT."

Transfer Agent and Registrar

   The transfer agent and registrar for the common stock is Harris Trust and
Savings Bank, 311 West Monroe Street, Chicago, Illinois 60606 (telephone number
(312) 461-4600).

                                       31
<PAGE>

                                  UNDERWRITING

   Under the terms and subject to the conditions contained in an underwriting
agreement dated February   , 2000, each underwriter named below has severally,
but not jointly, agreed to purchase from us the following respective numbers of
shares of Class A common stock:
<TABLE>
<CAPTION>
                                                                       Number of
                                                                        Shares
                                                                       ---------
                                Underwriter
      <S>                                                              <C>
      Credit Suisse First Boston Corporation.........................
                                                                       ---------
        Total........................................................  8,500,000
                                                                       =========
</TABLE>

   The underwriting agreement provides that the obligations of the underwriters
are subject to certain conditions precedent. The underwriters will be obligated
to purchase all of the shares of Class A common stock in this Offering other
than those shares covered by the over-allotment option described below, if any
are purchased. The underwriting agreement provides that, in the event of a
default by an underwriter, in certain circumstances the purchase commitments of
non-defaulting underwriters may be increased or the underwriting agreement may
be terminated.

   We have granted to the underwriters an option, expiring at the close of
business on the 30th day after the date of this document, to purchase an
aggregate of up to 1,275,000 additional shares of Class A common stock at the
offering price, less the underwriting discounts and commissions, all as set
forth on the cover page of this document. The underwriters may exercise this
option only to cover over-allotments in the sale of the shares of the Class A
common stock. To the extent the option is exercised, each underwriter will
become obligated, subject to certain conditions, to purchase approximately the
same percentage of additional shares of the Class A common stock as it was
obligated to purchase pursuant to the underwriting agreement.

   The representatives have advised us that the underwriters propose to offer
the shares to the public at the public offering price set forth on the cover
page of this document and, through the representatives, to selling group
members at such price less a concession of       per share, and the
underwriters and the selling group members may allow a discount of       per
share on sales to certain other broker dealers. After the public offering, the
representatives may change public offering price and concession and discount to
dealers.

   The following table summarizes the compensation we will pay to the
underwriters and the expenses payable by us.

                                       32
<PAGE>

<TABLE>
<CAPTION>
                                    Per Share                       Total
                          ----------------------------- -----------------------------
                             Without          With         Without          With
                          Over-allotment Over-allotment Ove-rallotment Over-allotment
                          -------------- -------------- -------------- --------------
<S>                       <C>            <C>            <C>            <C>
Underwriting discounts
 and commissions paid by
 us.....................       --             --             --             --
Expenses payable by us..       --             --             --             --
</TABLE>

   We, our officers and directors, and certain other holders of common stock
have agreed that, for a period of 45 days after the date of this document, they
will not publicly offer, sell, contract to sell, pledge or otherwise dispose
of, directly or indirectly, or file with the SEC a registration statement under
the Securities Act relating to, any additional shares of its Class A common
stock, or securities convertible into or exchangeable or exercisable for any
shares of its Class A common stock, or publicly disclose the intention to make
any such offer, sale, pledge, disposal or filing, without the prior written
consent of Credit Suisse First Boston Corporation, except with respect to
certain hedging transactions which two of those holders may enter into.

   We have agreed to indemnify the underwriters against certain liabilities
under the Securities Act, or contribute to payments which the underwriters may
be required to make in respect thereof.

   Certain of the underwriters engage in transactions with, and from time to
time have performed services for us and our subsidiaries in the ordinary course
of business. Credit Suisse First Boston Corporation acted as private placement
agent and as investor in the interim preferred stock financing in June 1998 and
as one of the representatives of the underwriters in our public common stock
offerings in July 1998 and February 1999, purchased 500,000 shares of Class A
common stock at the then current market price in a private placement in
February 1999, and was one of the initial purchasers in the notes placement in
October 1999. Certain of the other underwriters participated as representatives
in our public offerings in July 1998 and February 1999 and as initial
purchasers in our notes placement.

   The representatives, on behalf of the underwriters, may engage in over-
allotment, stabilizing transactions, syndicate covering transactions, penalty
bids and "passive" market making in accordance with Regulation M under the
Securities Exchange Act of 1934. Over-allotment involves syndicate sales in
excess of the offering size, which creates a syndicate short position.
Stabilizing transactions permit bids to purchase the underlying security so
long as the stabilizing bids do not exceed a specified maximum. Syndicate
covering transactions involve purchases of the Class A common stock in the open
market after the distribution has been completed in order to cover syndicate
short positions. Penalty bids permit the representatives to reclaim a selling
concession from a syndicate member when shares of the Class A common stock
originally sold by such syndicate member are purchased in a syndicate covering
transaction to cover syndicate short positions. In "passive" market making,
market makers in the Class A common stock who are underwriters or prospective
underwriters may, subject to certain limitations, make bids for or purchases of
the Class A common stock until the time, if any, at which a stabilizing bid is
made. Such stabilizing transactions, syndicate covering transactions and
penalty bids may cause the price of the Class A common stock to be higher than
it would otherwise be in the absence of such transactions. These transactions
may be effected on the NYSE or otherwise and, if commenced, may be discontinued
at any time.

   The Class A common stock is traded on the NYSE under the symbol "AMT".

                                       33
<PAGE>

                          NOTICE TO CANADIAN RESIDENTS

Resale Restrictions

   The distribution of the Class A common stock in Canada is being made only on
a private placement basis exempt from the requirement that we prepare and file
a prospectus with the securities regulatory authorities in each province where
trades of the Class A common stock are effected. Accordingly, any resale of the
Class A common stock in Canada must be made in accordance with applicable
securities laws which will vary depending on the relevant jurisdiction. These
may require resales to be made in accordance with available statutory
exemptions or pursuant to a discretionary exemption granted by the applicable
Canadian securities regulatory authority. Purchasers are advised to seek legal
advice prior to any resale of the Class A common stock.

Representatives of Purchasers

   Each purchaser of the Class A common stock in Canada who receives a purchase
confirmation will be deemed to represent to us and the dealer from whom such
purchase confirmation is received that (a) that purchaser is entitled under
applicable provincial securities laws to purchase each share of Class A common
stock without the benefit of a prospectus qualified under such securities laws,
(b) where required by law, that such purchaser is purchasing as principal and
not as agent, and (c) such purchaser has reviewed "--Resale Restrictions"
above.

Rights of Action (Ontario Purchasers)

   The securities being offered are those of a foreign issuer and Ontario
purchasers will not receive the contractual right of action prescribed by
section 32 of the Regulation under the Securities Act (Ontario). As a result,
Ontario purchasers must rely on other remedies that may be available, including
common law rights of action for damages or rescission or rights of action under
the civil liability provisions of the U.S. federal securities laws.

Enforcement of Legal Rights

   All of the issuer's directors and officers as well as the experts named in
this document may be located outside of Canada. As a result, Canadian
purchasers may not be able to effect service of process within Canada upon the
issuer or any of those persons. All or a substantial portion of the assets of
the issuer and those persons may be located outside of Canada. As a result, a
judgment may not be satisfiable against the issuer or those persons in Canada
or a judgment obtained in Canadian courts may not be enforceable against the
issuer or those persons outside of Canada.

Notice to British Columbia Residents

   A purchaser of the Class A common stock to whom the Securities Act (British
Columbia) applies is required to file with the British Columbia Securities
Commission a report within ten days of the sale of any Class A Common Stock
acquired by that purchaser pursuant to this Offering. The report must be in the
form attached to British Columbia Securities Commission Blanket Order BOR
#95/17, a copy of which may be obtained from us. Only one report must be filed
in respect of the Class A common stock acquired on the same date and under the
same prospectus exemption.

Taxation and Eligibility for Investment

   Canadian purchasers of Class A common stock should consult their own legal
and tax advisors with respect to the tax consequences of an investment in the
Class A common stock in their particular circumstances and with respect to the
eligibility of the Class A common stock for investment by the purchaser under
relevant Canadian legislation.

                                       34
<PAGE>

                             VALIDITY OF THE SHARES

   The validity of the shares of Class A common stock to be sold in this
offering have been passed upon for us by Sullivan & Worcester LLP, Boston,
Massachusetts, and for the underwriters by Sullivan & Cromwell, New York, New
York. Norman A. Bikales, a member of the firm of Sullivan & Worcester LLP, is
the owner of 11,000 shares of Class A common stock and 41,490 shares of Class B
common stock and has an option to purchase 20,000 shares of Class A common
stock at $10.00 per share. Mr. Bikales and/or associates of that firm serve as
our secretary or assistant secretaries and certain of our subsidiaries.

                                    EXPERTS

   The consolidated financial statements of American Tower Corporation as of
December 31, 1998 and 1997 and for each of the years in the three year period
ended December 31, 1998 incorporated by reference in this prospectus from the
Company's Annual Report on Form 10-K, have been audited by Deloitte & Touche
LLP, independent auditors, as stated in their report, which is incorporated
herein by reference, and has been so incorporated in reliance upon the report
of such firm given upon their authority as experts in accounting and auditing.

   The following financial statements are incorporated by reference in this
prospectus from the Form 8-K dated September 17, 1999:

  .  The consolidated financial statements of American Tower Corporation and
     subsidiaries as of December 31, 1997 and 1996, and for each of the years
     in the three year period ended December 31, 1997 have been incorporated
     by reference in this prospectus in reliance upon the report of KPMG LLP,
     independent auditors, incorporated by reference in this prospectus, and
     upon the authority of said firm as experts in accounting and auditing.

  .  The consolidated financial statements of OmniAmerica, Inc. and
     Subsidiaries (formerly Specialty Teleconstructors, Inc.) at and for the
     year ended June 30, 1998, incorporated by reference in this prospectus
     have been audited by Ernst & Young LLP, independent auditors, as stated
     in their report incorporated by reference herein, and are incorporated
     by reference herein in reliance upon such report given on the authority
     of such firm as experts in accounting and auditing.

  .  The consolidated financial statements of OmniAmerica, Inc. and
     Subsidiaries (formerly Specialty Teleconstructors, Inc.) as of and for
     the year ended June 30, 1997 have been incorporated by reference in this
     prospectus in reliance upon the report of KPMG LLP, independent
     auditors, incorporated by reference in this prospectus, and upon the
     authority of said firm as experts in accounting and auditing.

  .  The financial statements of Telecom Towers, LLC as of December 31, 1998
     and 1997 and for the year ended December 31, 1998 and the three month
     period from September 30, 1997 (date of inception) to December 31, 1997
     and the financial statements of Telecom Southwest Towers LP, Telecom
     Towers Mid-Atlantic LP, and Telecom Towers of the West, LP as of July
     31, 1998 and December 31, 1997 and for the seven month period ended July
     31, 1998 and the year ended December 31, 1997, incorporated by reference
     in this prospectus have been audited by Ernst & Young LLP, independent
     auditors, as stated in their reports appearing therein, and as to the
     seven month period ended July 31, 1998 and the year ended December 31,
     1997 as related to Telecom Towers Mid-Atlantic, LP and as to the year
     ended December 31, 1998 as related to Telecom Towers, LLC is based in
     part on the reports of KPMG LLP, independent auditors, as set forth in
     their reports on the financial statements of RCC Consultants, Inc. (not
     separately presented in the Form 8-K) appearing therein. The financial
     statements referred to above are included in reliance upon such reports
     given upon the authority of such firms as experts in accounting and
     auditing.

  .  The financial statements of Wauka Communications, Inc. as of October 26,
     1998 and December 31, 1997 and for the ten month period ended October
     26, 1998 and year ended December 31, 1997 incorporated by reference in
     this prospectus have been audited by Arthur Andersen LLP, independent
     auditors, as stated in their report appearing therein.

                                       35
<PAGE>

  .  The consolidated financial statements of UNIsite, Inc. and subsidiaries
     as of December 31, 1998 and 1997 and for each of the years in the three
     year period ended December 31, 1998 have been incorporated by reference
     in this prospectus in reliance upon the report of KPMG LLP, independent
     auditors, incorporated by reference in this prospectus, and upon the
     authority of said firm as experts in accounting and auditing.

                      WHERE YOU CAN FIND MORE INFORMATION

   We file annual, quarterly and current reports, proxy statements and other
information with the SEC. You may read and copy any reports, statements or
other information on file at the SEC's public reference room at 450 Fifth
Street, N.W., Washington, D.C. 20549. You can request copies of those documents
upon payment of a duplicating fee to the SEC. You may also review a copy of the
registration statement at the SEC's regional offices in Chicago, Illinois and
New York, New York. Please call the SEC at 1-800-SEC-0330 for further
information on the operation of the public reference rooms. You can review our
SEC filings and the registration statement by accessing the SEC's Internet site
at http://www.sec.gov.

   The SEC allows us to "incorporate by reference" the information we file with
them. This means that we can disclose important information to you by referring
you to those documents. The information incorporated by reference is considered
to be part of this prospectus. Statements in this prospectus regarding the
contents of any contract or other document may not be complete. You should
refer to the copy of the contract or other document filed as an exhibit to the
registration statement. Later information filed with the SEC will update and
supersede information we have included or incorporated by reference in this
prospectus.

   We incorporate by reference the documents listed below and any filings made
after the date of the original filing of the registration statement of which
this prospectus is a part made with the SEC under Section 13(a), 13(c), 14 or
15(d) of the Securities Exchange Act of 1934 until this offering is completed
or terminated:

  .  our Annual Report on Form 10-K for the fiscal year ended December 31,
     1998 (the "1998 Annual Report"),

  .  our proxy statement for our 1999 annual meeting of stockholders,

  .  our Quarterly Reports on Form 10-Q for the quarters ended March 31, June
     30, and September 30, 1999 (the "March 1999 Quarterly Report", the "June
     1999 Quarterly Report" and the "September 1999 Quarterly Report"), and

  .  (a) our Current Reports on Form 8-K dated January 8, 1999, January 21,
     1999, February 12, 1999, February 24, 1999, March 5, 1999, July 16,
     1999, September 17, 1999, September 21, 1999, November 15, 1999, January
     28, 2000, and January 31, 2000; and (b) our Current Reports on Form 8-
     K/A dated January 27, 1999 and March 18, 1999.

   We will provide a copy of the documents we incorporate by reference,
excluding exhibits other than those to which we specifically refer. You may
obtain this information at no cost by writing or telephoning us at: 116
Huntington Avenue, Boston, Massachusetts 02116, (617) 375-7500, Attention:
Director of Investor Relations.

                                       36
<PAGE>

                           AMERICAN TOWER CORPORATION

                       REGISTRATION STATEMENT ON FORM S-3

                                    PART II

                   INFORMATION NOT REQUIRED IN THE PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution.

   The following expenses are the estimated expenses of the issuance and
distribution of the securities (other than underwriting discounts and
commissions) being registered, all of which will be paid by American Tower:

<TABLE>
<S>                                                                    <C>
Securities and Exchange Commission fee................................ $118,837
New York Stock Exchange listing fee ($3,500 per 1.0 million shares)...   29,750
Accountants' fees and expenses........................................  150,000
Legal fees and expenses...............................................  150,000
Miscellaneous.........................................................   51,413
                                                                       --------
Total................................................................. $500,000
                                                                       ========
</TABLE>

   The foregoing, except for the SEC, NYSE and NASD fees, are estimated.

Item 15. Indemnification of Directors and Officers.

     Section 145 of the DGCL provides, in effect, that any person made a
  party to any action by reason of the fact that he is or was a director,
  officer, employee or agent of ATC may and, in certain cases, must be
  indemnified by ATC against, in the case of a non-derivative action,
  judgments, fines, amounts paid in settlement and reasonable expenses
  (including attorney's fees), if in either type of action he acted in good
  faith and in a manner he reasonably believed to be in or not opposed to the
  best interests of ATC and, in a non-derivative action, which involves a
  criminal proceeding, in which such person had no reasonable cause to
  believe his conduct was unlawful. This indemnification does not apply, in a
  derivative action, to matters as to which it is adjudged that the director,
  officer, employee or agent is liable to ATC, unless upon court order it is
  determined that, despite such adjudication of liability, but in view of all
  the circumstances of the case, he is fairly and reasonably entitled to
  indemnity for expenses.

   Article XII of ATC's By-Laws provides that ATC shall indemnify each person
who is or was an officer or director of ATC to the fullest extent permitted by
Section 145 of the DGCL.

     Article Sixth of ATC's Restated Certificate states than no director of
  ATC shall be personally liable to ATC or its stockholders for monetary
  damages for breach of fiduciary duty as a director, except for (i) breach
  of the director's duty of loyalty to ATC or its stockholders, (ii) acts or
  omissions not in good faith or which involve intentional misconduct or
  knowing violation of law, (iii) liability under Section 174 of the DGCL
  relating to certain unlawful dividends and stock repurchases, or (iv) any
  transaction from which the director derived an improper personal benefit.

Item 16. Exhibits.

   Listed below are the exhibits which are filed as part of this Registration
Statement on Form S-3 (according to the number assigned to them in Item 601 of
Regulation S-K).

<TABLE>
<CAPTION>
 Exhibit
   No.   Description of Document             Exhibit File No.
 ------- -----------------------             ----------------
 <C>     <C>                                 <S>
 1       Underwriting Agreement              Filed herewith as Exhibit 1
 5       Opinion of Sullivan & Worcester LLP Filed herewith as Exhibit 5
</TABLE>

                                      II-1
<PAGE>

<TABLE>
<CAPTION>
 Exhibit
   No.   Description of Document             Exhibit File No.
 ------- -----------------------             ----------------
 <C>     <C>                                 <S>
 23.1    Independent Auditors' Consent--
          Deloitte & Touche LLP              Filed herewith as Exhibit 23.1
 23.2    Consent of KPMG LLP                 Filed herewith as Exhibit 23.2
 23.3    Consent of KPMG LLP                 Filed herewith as Exhibit 23.3
 23.4    Consent of Ernst & Young LLP        Filed herewith as Exhibit 23.4
 23.5    Consent of Ernst & Young LLP        Filed herewith as Exhibit 23.5
 23.6    Consent of KPMG LLP                 Filed herewith as Exhibit 23.6
 23.7    Consent of Arthur Andersen LLP      Filed herewith as Exhibit 23.7
 23.8    Consent of KPMG LLP                 Filed herewith as Exhibit 23.8
 23.9    Consent of Sullivan & Worcester LLP Contained in the opinion of
                                              Sullivan & Worcester LLP filed
                                              herewith as Exhibit 5
 24      Power of Attorney                   Filed herewith as page II-3 of
                                              the Registration Statement
</TABLE>

Item 17. Undertakings.

   (a) Insofar as indemnification for liabilities arising under the Securities
Act of 1933 may be permitted to directors, officers and controlling persons of
the Registrant pursuant to the provisions referred to in Item 15 of this
registration statement, or otherwise, the Registrant has been advised that in
the opinion of the Securities and Exchange Commission such indemnification is
against public policy as expressed in the Securities Act and is, therefore,
unenforceable. In the event that a claim for indemnification against such
liabilities (other than the payment by the Registrant of expenses incurred or
paid by a director, officer or controlling person of the Registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the Registrant will, unless in the opinion of its counsel the
matter has been settled by controlling precedent, submit to a court of
appropriate jurisdiction the question whether such indemnification by it is
against public policy as expressed in the Securities Act and will be governed
by the final adjudication of such issue.

   (b) The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
registrant's annual report pursuant to section 13(a) or section 15(d) of the
Securities Exchange Act of 1934 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered herein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

                                      II-2
<PAGE>

                                   SIGNATURES

   Pursuant to the requirements of the Securities Act, the Company certifies
that it has reasonable grounds to believe that it meets all of the requirements
for filing on Form S-3 and has duly caused this registration statement to be
signed on its behalf by the undersigned, thereunto duly authorized, in the City
of Boston, Commonwealth of Massachusetts, on the 31st day of January, 2000.

                                          American Tower Corporation

                                                  /s/ Steven B. Dodge
                                          By: _________________________________
                                                      Steven B. Dodge
                                              Chairman of the Board, President
                                                and Chief Executive Officer

   The undersigned Officers and Directors of American Tower Corporation (the
"Company") hereby severally constitute Joseph L. Winn, Justin D. Benincasa,
Jonathan R. Black and Norman A. Bikales, and each of them, acting singly, our
true and lawful attorneys to sign for us and in our names in the capacities
indicated below the Company's Registration Statement on Form S-3 relating to
the registration of such securities under the Securities Act of 1933, as
amended, and any and all amendments thereto, including without limitation any
registration statement or post-effective amendment thereof filed under and
meeting the requirements of rule 462(b) under the Securities Act, hereby
ratifying and confirming our signatures as they may be signed by our attorneys
to such Registration Statement and any and all amendments thereto.

   Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons on behalf
of the Company and in the capacities and on the dates indicated.

<TABLE>
<CAPTION>
              Signature                          Title                   Date
              ---------                          -----                   ----

<S>                                    <C>                        <C>
       /s/ Steven B. Dodge             Chairman, President, Chief  January 31, 2000
______________________________________  Executive Officer and
           Steven B. Dodge              Director

        /s/ Joseph L. Winn             Chief Financial Officer     January 31, 2000
______________________________________  and Treasurer
            Joseph L. Winn

     /s/ Justin D. Benincasa           Vice President and          January 31, 2000
______________________________________  Corporate Controller
         Justin D. Benincasa

         /s/ Alan L. Box               Director                    January 31, 2000
______________________________________
             Alan L. Box

      /s/ Arnold L. Chavkin            Director                    January 31, 2000
______________________________________
          Arnold L. Chavkin

        /s/ Dean H. Eisner             Director                    January 31, 2000
______________________________________
            Dean H. Eisner
</TABLE>

                                      II-3
<PAGE>

<TABLE>
<CAPTION>
              Signature                          Title                   Date
              ---------                          -----                   ----

<S>                                    <C>                        <C>
        /s/ Jack D. Furst              Director                    January 31, 2000
______________________________________
            Jack D. Furst

    /s/ J. Michael Gearon, Jr.         Director                    January 31, 2000
______________________________________
        J. Michael Gearon, Jr.

        /s/ Fred R. Lummis             Director                    January 31, 2000
______________________________________
            Fred R. Lummis

         /s/ Randall Mays              Director                    January 31, 2000
______________________________________
             Randall Mays

       /s/ Thomas H. Stoner            Director                    January 31, 2000
______________________________________
           Thomas H. Stoner

      /s/ Maggie Wilderotter           Director                    January 31, 2000
______________________________________
          Maggie Wilderotter
</TABLE>

                                      II-4
<PAGE>

                                 EXHIBIT INDEX

   Listed below are the exhibits which are filed as part of this Registration
Statement on Form S-3 (according to the number assigned to them in Item 601 of
Regulation S-K).

<TABLE>
<CAPTION>
 Exhibit
   No.   Description of Document             Exhibit File No.
 ------- -----------------------             ----------------
 <C>     <C>                                 <S>
 1       Underwriting Agreement              Filed herewith as Exhibit 1
 5       Opinion of Sullivan & Worcester LLP Filed herewith as Exhibit 5
 23      Consent of Sullivan & Worcester LLP Contained in the opinion of
                                              Sullivan & Worcester LLP filed
                                              herewith as Exhibit 5
 23.1    Independent Auditors' Consent--
          Deloitte & Touche LLP              Filed herewith as Exhibit 23.1
 23.2    Consent of KPMG LLP                 Filed herewith as Exhibit 23.2
 23.3    Consent of KPMG LLP                 Filed herewith as Exhibit 23.3
 23.4    Consent of Ernst & Young LLP        Filed herewith as Exhibit 23.4
 23.5    Consent of Ernst & Young LLP        Filed herewith as Exhibit 23.5
 23.6    Consent of KPMG LLP                 Filed herewith as Exhibit 23.6
 23.7    Consent of Arthur Andersen LLP      Filed herewith as Exhibit 23.7
 23.8    Consent of KPMG LLP                 Filed herewith as Exhibit 23.8
 24      Power of Attorney                   Filed herewith as page II-3 of the
                                              Registration Statement
</TABLE>

<PAGE>

                                                                       EXHIBIT 1
                                                       Draft of January 27, 2000


                                8,500,000 SHARES

                           AMERICAN TOWER CORPORATION

                 CLASS A COMMON STOCK, PAR VALUE $.01 PER SHARE


                             UNDERWRITING AGREEMENT
                             ----------------------


                                              February   , 2000



Credit Suisse First Boston Corporation,



As Representatives of the Several Underwriters (the "Representatives"),
c/o Credit Suisse First Boston Corporation,
Eleven Madison Avenue,
New York, N.Y. 10010-3629.

Dear Sirs:

          1.  Introductory.  American Tower Corporation, a Delaware corporation
("Company"), proposes to issue and sell 8,500,000 shares ("Firm Securities") of
its Class A Common Stock, par value $.01 per share ("Class A Common Stock" or
"Securities").  The Company also proposes to sell to the Underwriters, at the
option of the Underwriters, an aggregate of not more than 1,275,000 additional
shares ("Optional Securities") of its Securities, as set forth below. The Firm
Securities and the Optional Securities are herein collectively called the
"Offered Securities".  The Company hereby agrees with the several Underwriters
named in Schedule A hereto ("Underwriters") as hereinafter set forth.


          2.  Representations and Warranties of the Company. The Company
represents and warrants to, and agrees with, the several Underwriters that:

          (a) A registration statement (No. 333-      ) on Form S-3 relating to
     the Offered Securities, including a form of prospectus, has been filed with
     the Securities and Exchange Commission ("Commission") and either (A) has
     been declared effective under the Securities Act of 1933 (the "Act") and is
     not proposed to be amended or (B) is proposed to be amended by amendment or
     post-effective amendment. If such registration statement (the "initial
     registration statement") has been declared effective, either (A) an
     additional registration statement (the "additional registration

                                       1
<PAGE>

     statement") relating to the Offered Securities may have been filed with the
     Commission pursuant to Rule 462(b) ("Rule 462(b)") under the Act and, if so
     filed, has become effective upon filing pursuant to such Rule and the
     Offered Securities all have been duly registered under the Act pursuant to
     the initial registration statement and, if applicable, the additional
     registration statement or (B) such an additional registration statement is
     proposed to be filed with the Commission pursuant to Rule 462(b) and will
     become effective upon filing pursuant to such Rule and upon such filing the
     Offered Securities will all have been duly registered under the Act
     pursuant to the initial registration statement and such additional
     registration statement. If the Company does not propose to amend the
     initial registration statement or if an additional registration statement
     has been filed and the Company does not propose to amend it, and if any
     post-effective amendment to either such registration statement has been
     filed with the Commission prior to the execution and delivery of this
     Agreement, the most recent amendment (if any) to each such registration
     statement has been declared effective by the Commission or has become
     effective upon filing pursuant to Rule 462(c) ("Rule 462(c)") under the Act
     or, in the case of the additional registration statement, Rule 462(b). For
     purposes of this Agreement, "Effective Time" with respect to the initial
     registration statement or, if filed prior to the execution and delivery of
     this Agreement, the additional registration statement means (A) if the
     Company has advised the Representatives that it does not propose to amend
     such registration statement, the date and time as of which such
     registration statement, or the most recent post-effective amendment thereto
     (if any) filed prior to the execution and delivery of this Agreement, was
     declared effective by the Commission or has become effective upon filing
     pursuant to Rule 462(c), or (B) if the Company has advised the
     Representatives that it proposes to file an amendment or post-effective
     amendment to such registration statement, the date and time as of which
     such registration statement, as amended by such amendment or post-effective
     amendment, as the case may be, is declared effective by the Commission. If
     an additional registration statement has not been filed prior to the
     execution and delivery of this Agreement but the Company has advised the
     Representatives that it proposes to file one, "Effective Time" with respect
     to such additional registration statement means the date and time as of
     which such registration statement is filed and becomes effective pursuant
     to Rule 462(b). "Effective Date" with respect to the initial registration
     statement or the additional registration statement (if any) means the date
     of the Effective Time thereof. The initial registration statement, as
     amended at its Effective Time, including all material incorporated by
     reference therein, including all information contained in the additional
     registration statement (if any) and deemed to be a part of the initial
     registration statement as of the Effective Time of the additional
     registration statement pursuant to the General Instructions of the Form on
     which it is filed and including all information (if any) deemed to be a
     part of the initial registration statement as of its Effective Time
     pursuant to Rule 430A(b) ("Rule 430A(b)") under the Act, is hereinafter
     referred to as the "Initial Registration Statement". The additional
     registration statement, as amended at its Effective Time, including the
     contents of the initial registration statement incorporated by reference
     therein and including all information (if any) deemed to be a part of the
     additional registration statement as of its Effective Time pursuant to Rule
     430A(b), is hereinafter referred to as the "Additional Registration
     Statement". The Initial Registration Statement and the Additional
     Registration Statement are hereinafter referred to collectively as the
     "Registration Statements" and individually as a "Registration Statement".
     The form of prospectus relating to the Offered Securities, as first filed
     with the Commission pursuant to and in accordance with Rule 424(b) ("Rule
     424(b)") under the Act or (if no such filing is required) as included in a
     Registration Statement, including all material incorporated by reference in
     such prospectus, is hereinafter referred to as the "Prospectus". No
     document has been or will be prepared or distributed in reliance on Rule
     434 under the Act.

          (b) If the Effective Time of the Initial Registration Statement is
     prior to the execution and delivery of this Agreement: (A) on the Effective
     Date of the Initial Registration Statement, the Initial Registration
     Statement conformed in all material respects to the requirements of the Act
     and the rules and regulations of the Commission ("Rules and Regulations")
     and did not include any untrue

                                       2
<PAGE>

     statement of a material fact or omit to state any material fact required to
     be stated therein or necessary to make the statements therein not
     misleading, (B) on the Effective Date of the Additional Registration
     Statement (if any), each Registration Statement conformed, or will conform,
     in all material respects to the requirements of the Act and the Rules and
     Regulations and did not include, or will not include, any untrue statement
     of a material fact and did not omit, or will not omit, to state any
     material fact required to be stated therein or necessary to make the
     statements therein not misleading, and (C) on the date of this Agreement,
     the Initial Registration Statement and, if the Effective Time of the
     Additional Registration Statement is prior to the execution and delivery of
     this Agreement, the Additional Registration Statement each conforms, and at
     the time of filing of the Prospectus pursuant to Rule 424(b) or (if no such
     filing is required) at the Effective Date of the Additional Registration
     Statement in which the Prospectus is included, each Registration Statement
     and the Prospectus will conform, in all material respects to the
     requirements of the Act and the Rules and Regulations, and neither of such
     documents includes, or will include, any untrue statement of a material
     fact or omits, or will omit, to state any material fact required to be
     stated therein or necessary to make the statements therein not misleading.
     If the Effective Time of the Initial Registration Statement is subsequent
     to the execution and delivery of this Agreement: on the Effective Date of
     the Initial Registration Statement, the Initial Registration Statement and
     the Prospectus will conform in all material respects to the requirements of
     the Act and the Rules and Regulations, neither of such documents will
     include any untrue statement of a material fact or will omit to state any
     material fact required to be stated therein or necessary to make the
     statements therein not misleading (in light of the circumstances under
     which it was made, in the case of the Prospectus), and no Additional
     Registration Statement has been or will be filed. The two preceding
     sentences do not apply to statements in or omissions from a Registration
     Statement or the Prospectus based upon written information furnished to the
     Company by any Underwriter through the Representatives specifically for use
     therein.

          (c) The Company has been duly incorporated and is an existing
     corporation in good standing under the laws of the State of Delaware, with
     power and authority (corporate and other) to own its properties and conduct
     its business as described in the Prospectus; and the Company is duly
     qualified to do business as a foreign corporation in good standing in all
     other jurisdictions in which its ownership or lease of property or the
     conduct of its business requires such qualification.

          (d) Each subsidiary of the Company has been duly incorporated (or
     formed, as the case may be) and is an existing corporation (or limited
     partnership or limited liability company, as the case may be) in good
     standing under the laws of the jurisdiction of its incorporation or
     formation, with power and authority (corporate and other) to own its
     properties and conduct its business as described in the Prospectus; and
     each subsidiary of the Company is duly qualified to do business as a
     foreign corporation in good standing in all other jurisdictions in which
     its ownership or lease of property or the conduct of its business requires
     such qualification except where failure to so qualify would not,
     individually or in the aggregate have a material adverse effect on the
     Company and its subsidiaries taken as a whole; all of the issued and
     outstanding capital stock (or partnership or other equity interests) of
     each subsidiary of the Company has been duly authorized and validly issued
     and is fully paid (except for any general partnership interest) and
     nonassessable; and, except for the pledge pursuant to the Credit Agreements
     (as defined herein) as disclosed in the Prospectus, the capital stock (and
     partnership and other equity interests) of each subsidiary owned by the
     Company, directly or through subsidiaries, is owned free from liens,
     encumbrances and defects.

          (e) The Company has full power and authority to authorize, issue and
     sell the Offered Securities as contemplated by this Agreement; the Offered
     Securities and all other outstanding shares of capital stock of the Company
     have been duly authorized; all outstanding shares of capital stock of the
     Company are, and, when the Offered Securities being sold by the Company
     have been delivered and paid for in accordance with this Agreement on each
     Closing Date (as defined below), such Offered Securities will have been,
     validly issued, fully paid and nonassessable, and conform or will

                                       3
<PAGE>

     conform to the descriptions  thereof  contained in the Prospectus; and the
     stockholders of the Company do not and will not have any preemptive rights
     with respect to any of such securities.

          (f) Except as disclosed in the Prospectus, there are no contracts,
     agreements or understandings between the Company and any person that would
     give rise to a valid claim against the Company or any Underwriter for a
     brokerage commission, finder's fee or other like payment in connection with
     the offering of the Offered Securities.

          (g) Except as disclosed in the Prospectus, there are no contracts,
     agreements or under standings between the Company and any person granting
     such person the right to require the Company to file a registration
     statement under the Act with respect to any outstanding securities of the
     Company owned or to be owned by such person or to require the Company to
     include such securities in the securities registered pursuant to a
     Registration Statement or in any securities being registered pursuant to
     any other registration statement filed by the Company under the Act.

          (h) The Offered Securities have been approved for listing, subject to
     notice of issuance, on the New York Stock Exchange ("NYSE").

          (i) No consent, approval, authorization, order or waiver of, or filing
     with, any governmental agency or body or any court is required to be
     obtained or made by the Company or any subsidiary of the Company for the
     consummation of the transactions contemplated by this Agreement in
     connection with the sale of the Offered Securities, except (i) such as have
     been obtained and made under the Act and (ii) such as may be required under
     state securities laws.

          (j) The execution, delivery and performance of this Agreement and the
     consummation of the transactions herein contemplated will not result in a
     breach or violation of any of the terms and provisions of, or constitute a
     default under, any statute, any rule, regulation, order or policy of any
     governmental agency or body or any court, domestic or foreign, having
     jurisdiction over the Company or any subsidiary of the Company or any of
     their properties, the Credit Agreements, each dated as of January 6, 2000,
     among ATC Teleports, Inc., American Towers, Inc. and American Tower L.P.,
     respectively, and  Toronto Dominion (Texas) Inc. as Administrative Agent,
     and the other lenders under each such agreement (as heretofore amended, the
     "Credit Agreements") or any other agreement or instrument to which the
     Company or any such subsidiary is a party or by which the Company or any
     such subsidiary is bound, or to which any of the properties of the Company
     or any such subsidiary is subject, or the charter or by-laws (or other
     constituent document) of the Company or any such subsidiary.

          (k) This Agreement has been duly authorized, executed and delivered by
     the Company.

          (l) Except as disclosed in the Prospectus or as would not,
     individually or in the aggregate have a material adverse effect on the
     Company or its subsidiaries taken as a whole, the Company and its
     subsidiaries have good and marketable title to all real properties and all
     other properties and assets owned by them, in each case free from liens,
     encumbrances and defects that would materially affect the value thereof or
     materially interfere with the use made or to be made thereof by them; and
     except as disclosed in the Prospectus, the Company and its subsidiaries
     hold any leased real or personal property under valid and enforceable
     leases with no exceptions that would materially interfere with the use made
     or to be made thereof by them.

          (m) The Company and its subsidiaries possess adequate certificates,
     authorities or permits issued by appropriate governmental agencies or
     bodies necessary to conduct the business now operated by them and have not
     received any notice of proceedings relating to the revocation or
     modification of any such certificate, authority or permit that, if
     determined adversely to the Company or any of its subsidiaries, would
     individually or in the aggregate have a material adverse effect on the

                                       4
<PAGE>

     condition (financial or other), business, properties or results of
     operations of the Company and its subsidiaries taken as a whole.


          (n) No labor dispute with the employees of the Company or any
     subsidiary exists or, to the knowledge of the Company, is imminent that
     might have a material adverse effect on the Company and its subsidiaries
     taken as a whole.

          (o) The Company and its subsidiaries own, possess or can acquire on
     reasonable terms, adequate trademarks, trade names and other rights to
     inventions, know-how, patents, copyrights, confidential information and
     other intellectual property (collectively, "intellectual property rights")
     necessary to conduct the business now operated by them, or presently
     employed by them, and have not received any notice of infringement of or
     conflict with asserted rights of others with respect to any intellectual
     property rights that, if determined adversely to the Company or any of its
     subsidiaries, would individually or in the aggregate have a material
     adverse effect on the Company and its subsidiaries taken as a whole.

          (p) Neither the Company nor any of its subsidiaries is in violation of
     any statute, any rule, regulation, decision or order of any governmental
     agency or body or any court, domestic or foreign, relating to the use,
     disposal or release of hazardous or toxic substances or relating to the
     protection or restoration of the environment or human exposure to hazardous
     or toxic substances (collectively, "environmental laws"), owns or operates
     any real property contaminated with any substance that is subject to any
     environmental laws, is liable for any off-site disposal or contamination
     pursuant to any environmental laws, or is subject to any claim relating to
     any environmental laws, which violation, contamination, liability or claim
     would individually or in the aggregate have a material adverse effect on
     the Company and its subsidiaries taken as a whole; and the Company is not
     aware of any pending investigation which might lead to such a claim.

          (q) There are no pending actions, suits or proceedings against or
     affecting the Company, any of its subsidiaries or any of their respective
     properties that, if determined adversely to the Company or any of its
     subsidiaries, would individually or in the aggregate have a material
     adverse effect on the condition (financial or other), business, prospects
     or results of operations of the Company and its subsidiaries taken as a
     whole, or would materially and adversely affect the ability of the Company
     to perform its obligations under this Agreement, or which are otherwise
     material in the context of the sale of the Offered Securities; and, except
     as disclosed in the Prospectus, no such actions, suits or proceedings are
     threatened or, to the Company's knowledge, contemplated.

          (r) The financial statements included or incorporated by reference in
     the Registration Statements and Prospectus present fairly the financial
     position of the Company and its consolidated subsidiaries and the other
     entities named therein as of the dates shown and their results of
     operations and cash flows for the periods shown, and such financial
     statements have been prepared in conformity with generally accepted
     accounting principles in the United States applied on a consistent basis;
     and the schedules included or incorporated  by reference in the
     Registration Statements present fairly the information required to be
     stated therein; and the assumptions used in preparing the pro forma
     financial information included or incorporated by reference in the
     Registration Statements and Prospectus provide a reasonable basis for
     presenting the significant effects directly attributable to the
     transactions or events described therein, the related pro forma adjustments
     give appropriate effect to those assumptions, and the pro forma columns
     therein reflect the proper application of those adjustments to the
     corresponding historical financial statement amounts.

          (s) Except as disclosed in the Prospectus, since the date of the
     latest audited financial statements included in the Prospectus there has
     been no material adverse change, nor any development or event involving a
     prospective material adverse change, in the condition (financial or other),
     business, properties or results of operations of the Company and its
     subsidiaries taken as a whole, and,

                                       5
<PAGE>

     except as disclosed in or contemplated by the Prospectus, there has been no
     dividend or distribution of any kind declared, paid or made by the Company
     on any class of its capital stock.

          (t) The Company is not and, after giving effect to the offering and
     sale of the Offered Securities and the application of the proceeds thereof
     as described in the Prospectus, will not be an "investment company" as
     defined in the Investment Company Act of 1940.

          3.  Purchase, Sale and Delivery of Offered Securities.  On the basis
of the representations, warranties and agreements herein contained, but subject
to the terms and conditions herein set forth, the Company agrees to sell to each
Underwriter, and each Underwriter agrees, severally and not jointly, to purchase
from the Company, at a purchase price of $            per share, the respective
number of shares of Firm Securities set forth opposite the names of the
Underwriters in Schedule A hereto.


          The Company will deliver the Firm Securities to the Representatives
for the accounts of the Underwriters, against payment of the purchase price in
Federal (same day) Funds by wire transfer in U.S. Dollars to an account at a
bank acceptable to CSFBC drawn to the order of the Company at the office of
Sullivan & Cromwell, 125 Broad Street, New York, New York at 9:30 A.M., New York
time, on February   , 2000 or at such other date and time not later than seven
full business days thereafter as CSFBC and the Company determine, such time
being herein referred to as the "First Closing Date."  For purposes of Rule
15c6-1 under the Securities Exchange Act of 1934, the First Closing Date (if
later than the otherwise applicable settlement date) shall be the settlement
date for payment of funds and delivery of securities for all the Offered
Securities sold pursuant to the offering. The certificates for the Firm
Securities so to be delivered will be in definitive form, in such denominations
and registered in such names as CSFBC requests and will be made available for
checking and packaging at the New York office of Harris Trust and Savings Bank
at least 24 hours prior to the First Closing Date.

          In addition, upon written notice from CSFBC given to the Company from
time to time not more than thirty days subsequent to the date of the Prospectus,
the Underwriters may purchase all or less than all of the Optional Securities at
the purchase price per share to be paid for the Firm Securities.  The Company
agrees to sell to the Underwriters the number of Optional Securities specified
in such notice and the Underwriters agree, severally and not jointly, to
purchase such Optional Securities.  Such Optional Securities shall be purchased
for the account of each Underwriter in the same proportion as the number of Firm
Securities set forth opposite such Underwriter's name bears to the total number
of Firm Securities (subject to adjustment by CSFBC to eliminate fractions) and
may be purchased by the Underwriters only for the purpose of covering over-
allotments made in connection with the sale of the Firm Securities.  No Optional
Securities shall be sold or delivered unless the Firm Securities previously have
been, or simultaneously are, sold and delivered.  The right to purchase the
Optional Securities or any portion thereof may be exercised from time to time
and to the extent not previously exercised may be surrendered and terminated at
any time upon notice by CSFBC to the Company.

          Each time for the delivery of and payment for the Optional Securities,
being herein referred to as an "Optional Closing Date", which may be the First
Closing Date (the First Closing Date and each Optional Closing Date, if any,
being sometimes referred to as a "Closing Date"), shall be determined by CSFBC
but shall not be later than seven full business days after written notice of
election to purchase Optional Securities is given. The Company will deliver the
Optional Securities being purchased on each Optional Closing Date to the
Representatives for the accounts of the several Underwriters, against payment of
the purchase price therefor in Federal (same day) Funds by wire transfer to an
account at a bank acceptable to CSFBC drawn to the order of the Company, at the
above office of Sullivan & Cromwell.  The certificates for the Optional
Securities being purchased on each Optional Closing Date will be in definitive
form, in such denominations and registered in such names as CSFBC requests upon
reasonable notice prior to such Optional Closing Date and will be made available
for checking and packaging at the New York office of Harris Trust and Savings
Bank at a reasonable time in advance of such Optional Closing Date.

                                       6
<PAGE>

          4.  Offering by Underwriters.  It is understood that the several
Underwriters propose to offer the Offered Securities for sale to the public as
set forth in the Prospectus.

          5.  Certain Agreements of the Company.  The Company agrees with the
several Underwriters that:

          (a) The Company will file the Prospectus with the Commission pursuant
     to and in accordance with subparagraph (1) (or, if applicable and if
     consented to by CSFBC, subparagraph (4)) of Rule 424(b) not later than the
     earlier of (A) the second business day following the execution and delivery
     of this Agreement or (B) the fifteenth business day after the Effective
     Date of the Initial Registration Statement.

          The Company will advise CSFBC promptly of any such filing pursuant to
     Rule 424(b).  If the Effective Time of the Initial Registration Statement
     is prior to the execution and delivery of this Agreement and an additional
     registration statement is necessary to register a portion of the Offered
     Securities under the Act but the Effective Time thereof has not occurred as
     of such execution and delivery, the Company will file the additional
     registration statement or, if filed, will file a post-effective amendment
     thereto with the Commission pursuant to and in accordance with Rule 462(b)
     on or prior to 10:00 P.M., New York time, on the date of this Agreement or,
     if earlier, on or prior to the time the Prospectus is printed and
     distributed to any Underwriter, or will make such filing at such later date
     as shall have been consented to by CSFBC.

          (b) The Company will advise CSFBC promptly of any proposal to amend or
     supplement the initial or any additional registration statement as filed or
     the related prospectus or the Initial Registration Statement, the
     Additional Registration Statement (if any) or the Prospectus and will not
     effect such amendment or supplementation without CSFBC's consent; and the
     Company will also advise CSFBC promptly of any amendment or supplementation
     of a Registration Statement or of the Prospectus and of the institution by
     the Commission of any stop order proceedings in respect of a Registration
     Statement and will use its best efforts to prevent the issuance of any such
     stop order and to obtain as soon as possible its lifting, if issued.

          (c) If, at any time when a prospectus relating to the Offered
     Securities is required to be delivered under the Act in connection with
     sales by any Underwriter or dealer, any event occurs as a result of which
     the Prospectus as then amended or supplemented would include an untrue
     statement of a material fact or omit to state any material fact necessary
     to make the statements therein, in the light of the circumstances under
     which they were made, not misleading, or if it is necessary at any time to
     amend the Prospectus to comply with the Act, the Company will promptly
     notify CSFBC of such event and will promptly prepare and file with the
     Commission, at its own expense, an amendment or supplement that will
     correct such statement or omission or an amendment that will effect such
     compliance.  Neither CSFBC's consent to, nor the Underwriters' delivery of,
     any such amendment or supplement shall constitute a waiver of any of the
     conditions set forth in Section 6.

          (d) As soon as practicable, but not later than the Availability Date
     (as defined below), the Company will make generally available to its
     securityholders an earnings statement covering a period of at least 12
     months beginning after the Effective Date of the Initial Registration
     Statement  which will satisfy the provisions of Section 11(a) of the Act.
     For the purpose of the preceding sentence, "Availability Date" means the
     45th day after the end of the fourth fiscal quarter following the fiscal
     quarter that includes the Effective Date, except that, if such fourth
     fiscal quarter is the last quarter of the Company's fiscal year,
     "Availability Date" means the 90th day after the end of such fourth fiscal
     quarter.

          (e) The Company will furnish to the Representatives copies of each
     Registration Statement (nine of which will be signed, or will be
     photocopies of signed ones in the case of the Initial

                                       7
<PAGE>

     Registration Statement, and will include all exhibits), each related
     preliminary prospectus and, so long as delivery of a prospectus relating to
     the Offered Securities is required to be delivered under the Act in
     connection with sales by any Underwriter or dealer, the Prospectus and all
     amendments and supplements to such documents, in each case as soon as
     available and in such quantities as CSFBC requests. The Company will pay
     the expenses of printing and distributing to the Underwriters all such
     documents.

          (f) The Company will arrange for the qualification of the Offered
     Securities for sale under the laws of such jurisdictions as CSFBC
     designates and will continue such qualifications in effect so long as
     required for the distribution; provided, that the Company shall not be
     required to qualify as a foreign corporation or to file a general consent
     to service of process or to subject itself to taxation generally in any
     jurisdiction.

          (g) During the period of five years hereafter, the Company will
     furnish to the Representatives and, upon request, to each of the other
     Underwriters, as soon as practicable after the end of each fiscal year, a
     copy of its annual report to stockholders for such year; and the Company
     will furnish to the Representatives (i) as soon as available, a copy of
     each report and any definitive proxy statement of the Company filed with
     the Commission under the Securities Exchange Act of 1934 or mailed to
     stockholders, and (ii) from time to time, such other information concerning
     the Company as CSFBC may reasonably request.

          (h) For a period of 45 days after the date of the initial public
     offering of the Offered Securities, the Company will not offer, sell,
     contract to sell, pledge or otherwise dispose of, directly or indirectly,
     or file with the Commission a registration statement under the Act relating
     to, any additional shares of its Securities, or securities convertible into
     or exchangeable or exercisable for any Securities, or disclose the
     intention to make any such offer, sale, pledge, disposal or filing, without
     the prior written consent of CSFBC, except with respect to private
     issuances of Securities (or securities convertible into or exchangeable for
     Securities) or in connection with acquisitions, if the holders thereof
     agree to be bound by the foregoing 45-day restriction to the same extent as
     the Company, grants of employee stock options pursuant to the terms of a
     plan in effect on the date hereof, issuances of Securities pursuant to the
     exercise of  stock options outstanding on the date hereof or granted
     pursuant to the terms of a plan in effect on the date hereof, issuances of
     Securities pursuant to any dividend reinvestment plan of the Company or
     issuances of Securities upon conversion of Class B Common Stock or Class C
     Common Stock.


     The Company agrees with the several Underwriters that the Company will pay
all expenses incident to the performance of its obligations under this
Agreement, and that the Company will reimburse the Underwriters (if and to the
extent incurred by them) for any filing fees and other expenses (including fees
and disbursements of counsel) incurred by them in connection with qualification
of the Offered Securities for sale under the laws of such jurisdictions as CSFBC
designates and the printing of memoranda relating thereto, for the filing fee of
the National Association of Securities Dealers, Inc. relating to the Offered
Securities, for any travel expenses of the Company's officers and employees and
any other expenses of the Company in connection with attending or hosting
meetings with prospective purchasers of the Offered Securities, and for expenses
incurred in distributing preliminary prospectuses and the Prospectus (including
any amendments and supplements thereto) to the Underwriters.


          6.  Conditions of the Obligations of the Underwriters.  The
obligations of the several Underwriters to purchase and pay for the Firm
Securities on the First Closing Date and the Optional Securities to be purchased
on each Optional Closing Date will be subject to the accuracy of the
representations and warranties on the part of the Company herein, to the
accuracy of the statements of Company officers made

                                       8
<PAGE>

     pursuant to the provisions hereof, to the performance by the Company of its
     obligations hereunder and to the following additional conditions precedent:

          (a) The Representatives shall have received a letter, dated the date
     of delivery thereof (which shall be on or prior to the date of this
     Agreement), of Deloitte & Touche LLP confirming that they are independent
     public accountants within the meaning of the Act and the applicable
     published Rules and Regulations thereunder and stating in effect that:

               (i)  in their opinion the financial statements and schedules
          examined by them and included or incorporated by reference in the
          Registration Statements comply in form in all material respects with
          the applicable accounting requirements of the Act and the related
          published Rules and Regulations;

               (ii)  they have performed the procedures specified by the
          American Institute of  Certified Public Accountants for a review of
          interim financial information as described in Statement of Auditing
          Standards No. 71, Interim Financial Information, on the unaudited
          financial statements included in the Registration Statements;

               (iii)  on the basis of the review referred to in clause (ii)
          above, a reading of the latest  available interim consolidated
          financial statements of the Company, inquiries of officials of the
          Company who have responsibility for financial and accounting matters
          and other specified procedures, nothing came to their attention that
          caused them to believe that:

               (A) the selected combined financial data included or incorporated
     by reference in the Prospectus for each of the five years ended December
     31, 1998 do not agree with, or were not properly derived from, the amounts
     set forth in each of the constituent companies' selected financial data
     included or incorporated by reference in the Prospectus for those same
     periods;

               (B) the selected financial data included or incorporated by
     reference in the Prospectus for each of the five years ended December 31,
     1998 do not agree with, or were not properly derived from, the amounts set
     forth in the audited financial statements of the Company for those same
     periods or were not determined on a basis substantially consistent with
     that of the corresponding amounts in the audited financial statements
     included or incorporated by reference in the Prospectus;

               (C) the unaudited financial statements included or incorporated
     by reference in the Registration Statements do not comply in form in all
     material respects with the applicable accounting requirements of the Act
     and the related published Rules and Regulations or any material
     modifications should be made to such unaudited financial statements for
     them to be in conformity with generally accepted accounting principles;

               (D) at the date of the latest available balance sheet read by
     such accountants, or at a subsequent specified date not more than five days
     prior to the date of this Agreement, there was any change in the capital
     stock or any increase in short-term debt or long-term debt of the Company
     and its consolidated subsidiaries or, at the date of the latest available
     balance sheet read by such accountants, there was any decrease in
     consolidated net current assets or net assets, as compared with amounts
     shown on the latest balance sheet included or incorporated by reference in
     the Prospectus;

               (E) for the period from the closing date of the latest statement
     of operations included or incorporated by reference in the Prospectus to
     the closing date of the latest available statement of operations read by
     such accountants there were

                                       9
<PAGE>

     any decreases, as compared with the corresponding period of the previous
     year and with the period of corresponding length ended the date of the
     latest Consolidated Statement of Operations included or incorporated by
     reference in the Prospectus, in consolidated net revenues, tower cash flow
     (as that term is defined in the Prospectus) or in other income and expense,
     net, or in the total or per share amounts of consolidated net income; or

               (F) the pro forma financial data set forth or incorporated by
     reference in the Prospectus does not comply in form in all material
     respects to the applicable accounting requirements of the Act and the
     related Rules and Regulations or the pro forma adjustments have not been
     properly applied to the historical amounts in the compilation of that data;
     except in all cases set forth in clauses (D) and (E) above for changes,
     increases or decreases which the Prospectus discloses have occurred or may
     occur or which are described in such letter; and

               (iv)  they have compared specified dollar amounts (or percentages
          derived from such  dollar amounts) and other financial information
          contained or incorporated by reference in the Registration Statements
          (in each case to the extent that such dollar amounts, percentages and
          other financial information are derived from the general accounting
          records of the Company, its subsidiaries and other entities whose
          financial statements are included or incorporated by reference in the
          Prospectus subject to the internal controls of the Company's or such
          entities' accounting system or are derived directly from such records
          by analysis or computation) with the results obtained from inquiries,
          a reading of such general accounting records and other procedures
          specified in such letter and have found such dollar amounts,
          percentages and other financial information to be in agreement with
          such results, except as otherwise specified in such letter.

               For purposes of this subsection, (i) if the Effective Time of the
          Initial Registration Statement is subsequent to the execution and
          delivery of this Agreement, "Registration Statements" shall mean the
          initial registration statement as proposed to be amended by the
          amendment or post-effective amendment to be filed shortly prior to its
          Effective Time, (ii) if the Effective Time of the Initial Registration
          Statement is prior to the execution and delivery of this Agreement but
          the Effective Time of the Additional Registration is subsequent to
          such execution and delivery, "Registration Statements" shall mean the
          Initial Registration Statement and the additional registration
          statement as proposed to be filed or as proposed to be amended by the
          post-effective amendment to be filed shortly prior to its Effective
          Time, and (iii) "Prospectus" shall mean the prospectus included in the
          Registration Statements.  All financial statements and schedules
          included in material incorporated by reference into the Prospectus
          shall be deemed included in the Registration Statements for purposes
          of this subsection.

          (b) The Representatives shall have received letters, dated the date of
     delivery thereof (which shall be on or prior to the date of this
     Agreement), of KPMG LLP, Arthur Andersen LLP and Ernst & Young LLP, in each
     case confirming that they are independent public accountants within the
     meaning of the Act and the applicable Rules and Regulations thereunder, and
     stating in effect that:


               (i)  in their opinion the financial statements and schedules
          examined by them and  included in the Registration Statements comply
          in form in all material respects with the applicable accounting
          requirements of the Act and the related published Rules and
          Regulations;

               (ii)  on the basis of a reading of the latest available interim
          consolidated financial  statements of the Company, inquiries of
          officials of the Company who have responsibility for

                                       10
<PAGE>

     financial and accounting matters and other specified procedures, nothing
     came to their attention that caused them to believe that:

                    (A)  the unaudited financial statements included or
               incorporated by reference  in the Registration Statements do not
               comply in form in all material respects with the applicable
               accounting requirements of the Act and the related published
               Rules and Regulations or any material modifications should be
               made to such unaudited financial statements for them to be in
               conformity with generally accepted accounting principles;

                    (B)  at the date of the latest available balance sheet read
               by such accountants,  or at a subsequent specified date not more
               than five days prior to the date of this Agreement, there was any
               change in the capital stock or any increase in short-term debt or
               long-term debt of the Company and its consolidated subsidiaries
               or, at the date of the latest available balance sheet read by
               such accountants, there was any decrease in consolidated net
               current assets or net assets, as compared with amounts shown on
               the latest balance sheet included or incorporated by reference in
               the Prospectus;

                    (C)  for the period from the closing date of the latest
               statement of operations  included or incorporated by reference in
               the Prospectus to the closing date of the latest available
               statement of operations read by such accountants there were any
               decreases, as compared with the corresponding period of the
               previous year and with the period of corresponding length ended
               the date of the latest Consolidated Statement of Operations
               included or incorporated by reference in the Prospectus, in
               consolidated net revenues, operating income (defined as net
               revenues less operating expenses, excluding depreciation,
               amortization and corporate expenses) or in other income and
               expense, net, or in the total or per share amounts of
               consolidated net income;

          except in all cases set forth in clauses (B) and (C) above for
          changes, increases or decreases which the Prospectus discloses have
          occurred or may occur or which are described in such letter; and

               (iii)  they have compared specified dollar amounts (or
          percentages derived from such  dollar amounts) and other financial
          information contained in the Registration Statements (in each case to
          the extent that such dollar amounts, percentages and other financial
          information are derived from the general accounting records of the
          entity whose financial statements they have audited subject to the
          internal controls of such entity's accounting system or are derived
          directly from such records by analysis or computation) with the
          results obtained from inquiries, a reading of such general accounting
          records and other procedures specified in such letter and have found
          such dollar amounts, percentages and other financial information to be
          in agreement with such results, except as otherwise specified in such
          letter.

          (c) The Prospectus shall have been filed with the Commission in
     accordance with the Rules and Regulations and Section 5(a) of this
     Agreement.  Prior to such Closing Date, no stop order suspending the
     effectiveness of either Registration Statement shall have been issued and
     no proceedings for that purpose shall have been instituted or, to the
     knowledge of the Company or the Representatives, shall be contemplated by
     the Commission.

          (d) Subsequent to the execution and delivery of this Agreement, there
     shall not have occurred (i) any change, or any development or event
     involving a prospective change, in the condition (financial or other),
     business, properties or results of operations of the Company or any of its
     subsidiaries which, in the judgment of a majority in interest of the
     Underwriters including the

                                       11
<PAGE>

     Representatives, is material and adverse and makes it impractical or
     inadvisable to proceed with completion of the public offering or the sale
     of and payment for the Offered Securities; (ii) any downgrading in the
     rating of any debt securities of the Company, by any "nationally recognized
     statistical rating organization" (as defined for purposes of Rule 436(g)
     under the Act), or any public announcement that any such organization has
     under surveillance or review its rating of any debt securities of the
     Company (other than an announcement with positive implications of a
     possible upgrading, and no implication of a possible downgrading, of such
     rating); (iii) any suspension or limitation of trading in securities
     generally on the New York Stock Exchange, or any setting of minimum prices
     for trading on such exchange, or any suspension of trading of any
     securities of the Company on any exchange or in the over-the-counter
     market; (iv) any banking moratorium declared by Federal or New York
     authorities; or (v) any outbreak or escalation of major hostilities in
     which the United States is involved, any declaration of war by Congress or
     any other substantial national or international calamity or emergency if,
     in the judgment of a majority in interest of the Underwriters including the
     Representatives, the effect of any such outbreak, escalation, declaration,
     calamity or emergency makes it impractical or inadvisable to proceed with
     completion of the public offering or the sale of and payment for the
     Offered Securities.

          (e) The Representatives shall have received an opinion, dated such
     Closing Date, of Sullivan & Worcester LLP, counsel for the Company, to the
     effect that:

               (i)  Each of the Company and the subsidiaries listed on Annex I
          hereto has been duly incorporated (or formed, as the case may be) and
          each of the Company and its subsidiaries is an existing corporation
          (or limited partnership or limited liability company, as the case may
          be) in good standing under the laws of the jurisdiction of its
          incorporation or formation, with corporate, partnership or limited
          liability company power and authority to own its properties and
          conduct its business as described in the Prospectus, and is duly
          qualified to do business as a foreign corporation (or other entity) in
          good standing in all other jurisdictions in which its ownership or
          lease of property or the conduct of its business requires such
          qualification, except where the failure to be so qualified would not
          individually or in the aggregate have a material adverse effect on the
          Company and its subsidiaries taken as a whole;

               (ii) The Company has full power and authority to authorize, issue
          and sell the Offered Securities as contemplated by this Agreement; the
          Offered Securities delivered on such Closing Date and all other
          outstanding shares of all classes of the capital stock of the Company
          have been duly authorized and validly issued, are fully paid and
          nonassessable and conform to the description thereof contained in the
          Prospectus under the caption "Description of Capital Stock"; and the
          stockholders of the Company have no preemptive rights with respect to
          the Offered Securities;

               (iii)  Except as described in the Prospectus, there are no
          contracts, agreements or understandings known to such counsel between
          the Company and any person granting such person the right to require
          the Company to file a registration statement under the Act with
          respect to any securities of the Company owned or to be owned by such
          person or to require the Company to include such securities in the
          securities registered pursuant to the Registration Statement or in any
          securities being registered pursuant to any other registration
          statement filed by the Company under the Act;

               (iv)  No consent, approval, authorization, order or waiver of, or
          filing with, any governmental agency or body or any court is required
          to be obtained or made by the Company for the consummation of the
          transactions contemplated by this Agreement in connection with the
          sale of the Offered Securities, except such counsel need not express
          any opinion as to (x) such as may be required under the Communications
          Act of 1934, as

                                       12
<PAGE>

          amended (the "Communications Act"), and (y) such as may be required by
          the Blue Sky laws of the several states of the United States;

               (v)  The execution, delivery and performance of this Agreement
          and the consummation of the transactions herein or therein
          contemplated will not result in a breach or violation of any of the
          terms and provisions of, or constitute a default under, any statute,
          any rule, regulation or order of any governmental agency or body or
          any court having jurisdiction over the Company, or any subsidiary of
          the Company or any of their properties, or, to such counsel's
          knowledge, any agreement or instrument to which the Company or any
          subsidiary of the Company is a party or by which the Company or any
          subsidiary of the Company is bound including, but not limited to, the
          Credit Agreements and the Registration Rights Agreement, dated as of
          February 25, 1999 and as subsequently amended, among the Company and
          the stockholders named therein, or to which any of the properties of
          the Company or any subsidiary of the Company is subject, or the
          charter or by-laws or other constituent document of the Company or any
          subsidiary of the Company, except that such counsel need not express
          any opinion with respect to the Communications Act or the rules,
          regulations and orders of the Federal Communications Commission (the
          "FCC") promulgated thereunder;

               (vi)  The Initial Registration Statement was declared effective
          under the Act as of the date and time specified in such opinion, the
          Additional Registration Statement (if applicable), satisfying the
          requirements of Rule 462(b), was filed and became effective under the
          Act as of the date and (if determinable) time specified in such
          opinion, the Prospectus was filed with the Commission pursuant to the
          subparagraph of Rule 424(b) specified in such opinion on the date
          specified therein or was included in the Initial Registration
          Statement or the Additional Registration Statement (as the case may
          be), and, to the best of the knowledge of such counsel, no stop order
          suspending the effectiveness of a Registration Statement or any part
          thereof has been issued and no proceedings for that purpose have been
          instituted or are pending or contemplated under the Act, and each
          Registration Statement and the Prospectus, and each amendment or
          supplement thereto, as of their respective effective or issue dates,
          complied as to form in all material respects with the requirements of
          the Act and the Rules and Regulations; such counsel have no reason to
          believe that any part of a Registration Statement or any amendment
          thereto, as of its effective date or as of such Closing Date,
          contained any untrue statement of a material fact or omitted to state
          any material fact required to be stated therein or necessary to make
          the statements therein not misleading; or that the Prospectus or any
          amendment or supplement thereto, as of its issue date or as of such
          Closing Date, contained any untrue statement of a material fact or
          omitted to state any material fact necessary in order to make the
          statements therein, in the light of the circumstances under which they
          were made, not misleading; the descriptions in each Registration
          Statement and the Prospectus of statutes, legal and governmental
          proceedings and contracts and other documents are accurate in all
          material respects and fairly present the information required to be
          shown; and such counsel do not know of any legal or governmental
          proceedings required to be described in either Registration Statement
          or the Prospectus which are not described as required or of any
          contracts or documents of a character required to be described in
          either Registration Statement or the Prospectus or to be filed as
          exhibits to either Registration Statement which are not described and
          filed as required; it being understood that such counsel need express
          no opinion as to the financial statements and schedules or other
          financial data contained in either Registration Statement or the
          Prospectus, except that such counsel need not express any opinion with
          respect to the Communications Act or the rules, regulations and orders
          of the FCC promulgated thereunder; and

                                       13
<PAGE>

               (vii) This Agreement has been duly authorized, executed and
          delivered by the Company.

          (f) The Representatives shall have received an opinion, dated such
     Closing Date, of Michael Milsom, Esq., Vice President of the Company and
     Vice President and General Counsel of ATC Teleports, Inc., to the effect
     that:

               (i)   No consent, approval, authorization, order or waiver of, or
          filing with, the FCC under the Communications Act and the published
          policies, rules and regulations of the FCC is required to be obtained
          or made for the consummation of the transactions contemplated by this
          Agreement in connection with the sale of the Offered Securities where
          the failure to obtain such consent, approval, authorization, order or
          waiver or to make such filing would have a material adverse effect on
          the Company and its subsidiaries taken as a whole;

               (ii)  The execution, delivery and performance of this Agreement
          and the consummation of the transactions herein contemplated will not
          result in a breach or violation of any of the terms or provisions of,
          or constitute a default under (i) the Communications Act or any FCC
          regulation, rule, published policy or order that would have a material
          adverse effect on the Company and its subsidiaries taken as a whole;
          and

               (iii) To the knowledge of such counsel, there are no
          administrative or judicial proceedings pending before, or threatened
          by, the FCC with respect to the Company or any subsidiary of the
          Company, or any towers owned or operated by the Company or any
          subsidiary of the Company that, if determined adversely, could
          reasonably be expected to have a material adverse effect upon the
          Company and its subsidiaries taken as a whole.

          (g) The Representatives shall have received from Sullivan &
     Cromwell, counsel for the Underwriters, such opinion or opinions, dated
     such Closing Date, with respect to the incorporation of the Company, the
     validity of the Offered Securities delivered on such Closing Date, the
     Registration Statements, the Prospectus and other related matters as the
     Representatives may require, and the Company shall have furnished to such
     counsel such documents as they request for the purpose of enabling them to
     pass upon such matters.

          (h) The Representatives shall have received a certificate, dated such
     Closing Date, of the Chief Executive Officer of the Company and the Chief
     Financial Officer of the Company in which such officers, to the best of
     their knowledge after reasonable investigation, shall state that the
     representations and warranties of the Company in this Agreement are true
     and correct, that the Company has complied with all agreements and
     satisfied all conditions on its part to be performed or satisfied hereunder
     at or prior to such Closing Date, that no stop order suspending the
     effectiveness of any Registration Statement has been issued and no
     proceedings for that purpose have been instituted or are contemplated by
     the Commission, that, subsequent to the date of the most recent financial
     statements in the Prospectus, there has been no material adverse change,
     nor any development or event involving a prospective material adverse
     change, in the condition (financial or other), business, properties or
     results of operations of the Company and its subsidiaries taken as a whole
     except as set forth in or contemplated by the Prospectus or as described in
     such certificate, and that any additional Registration Statement was filed
     pursuant to Rule 462(b) under the Act, including payment of the applicable
     filing fee in accordance with Rule 111(a); such registration statement
     satisfied the requirements of subparagraphs (1) and (3) of Rule 462(b);
     such registration statement was filed prior to the time the Prospectus was
     printed and distributed; and no document has been prepared or distributed
     in reliance on Rule 434 under the Act.

          (i) The Representatives shall have received letters, dated such
     Closing Date, of Deloitte & Touche LLP, KPMG  LLP, Arthur Andersen LLP and
     Ernst & Young LLP which meets the requirements of subsections (a) and (b),
     respectively, of this Section, except that the specified date

                                       14
<PAGE>

     referred to in such subsections will be a date not more than five days
     prior to such Closing Date for the purposes of this subsection.

          (j) The Securities to be delivered on such Closing Date shall have
     been approved for listing on the NYSE, subject only to official notice of
     issuance.

          (k) On or prior to the date of this Agreement, the Representatives
     shall have received letters from each of the executive officers and
     directors of the Company agreeing not to offer, sell, pledge or otherwise
     dispose of Securities or certain related securities on such terms as the
     Company and Representatives shall have agreed.

The Company will furnish the Representatives with such conformed copies of such
opinions, certificates, letters and documents as the Representatives reasonably
request. CSFBC may in its sole discretion waive on behalf of the Underwriters
compliance with any conditions to the obligations of the Underwriters hereunder,
whether in respect of an Optional Closing Date or otherwise.

          7.  Indemnification and Contribution.  (a) The Company will indemnify
and hold harmless each Underwriter against any losses, claims, damages or
liabilities, joint or several, to which such Underwriter may become subject,
under the Act or otherwise, insofar as such losses, claims, damages or
liabilities (or actions in respect thereof) arise out of or are based upon any
untrue statement or alleged untrue statement of any material fact contained in
any Registration Statement, the Prospectus, or any amendment or supplement
thereto, or any related preliminary prospectus, or arise out of or are based
upon the omission or alleged omission to state therein a material fact required
to be stated therein or necessary to make the statements therein not misleading,
and will reimburse each Underwriter for any legal or other expenses reasonably
incurred by such Underwriter in connection with investigating or defending any
such loss, claim, damage, liability or action as such expenses are incurred;
provided, however, that the Company will not be liable in any such case to the
extent that any such loss, claim, damage or liability arises out of or is based
upon an untrue statement or alleged untrue statement in or omission or alleged
omission from any of such documents in reliance upon and in conformity with
written information furnished to the Company by any Underwriter through the
Representatives specifically for use therein, it being understood and agreed
that the only such information furnished by any Underwriter consists of the
information described as such in subsection (b) below.  The foregoing indemnity
agreement with respect to any untrue statement or omission in the Preliminary
Prospectus shall not inure to the benefit of any Underwriter from whom the
person asserting any such losses, claims, damages or liabilities purchased the
Offered Securities if a copy of the Prospectus (as then amended or supplemented
if the Company shall have furnished any amendments or supplements thereto) was
not sent or given by or on behalf of such Underwriter to such person at or prior
to the written confirmation of the sale of the Offered Securities to such
person, and the Prospectus (as amended or supplemented) would have cured the
defect giving rise to such losses, claims, damages or liabilities.

          (b) Each Underwriter will severally and not jointly indemnify and hold
harmless the Company against any losses, claims, damages or liabilities to which
the Company may become subject, under the Act or otherwise, insofar as such
losses, claims, damages or liabilities (or actions in respect thereof) arise out
of or are based upon any untrue statement or alleged untrue statement of any
material fact contained in any Registration Statement, the Prospectus, or any
amendment or supplement thereto, or any related preliminary prospectus, or arise
out of or are based upon the omission or the alleged omission to state therein a
material fact required to be stated therein or necessary to make the statements
therein not misleading, in each case to the extent, but only to the extent, that
such untrue statement or alleged untrue statement or omission or alleged
omission was made in reliance upon and in conformity with written information
furnished to the Company by such Underwriter through the Representatives
specifically for use therein, and will reimburse any legal or other expenses
reasonably incurred by the Company in connection with investigating or defending
any such loss, claim, damage, liability or action as such expenses are incurred,
it being understood and agreed that the only such information furnished by any
Underwriter consists of  the following information in the Prospectus furnished
on behalf of each Underwriter:  the concession and reallowance figures appearing
in

                                       15
<PAGE>

the [      ] paragraph under the caption "Underwriting," the information
regarding discretionary sales by Underwriters contained in the [         ]
paragraph under the caption "Underwriting," and the material relationship
disclosure appearing in the [       ] paragraph under the caption
"Underwriting."

          (c) Promptly after receipt by an indemnified party under this Section
of notice of the commencement of any action, such indemnified party will, if a
claim in respect thereof is to be made against an indemnifying party under
subsection (a) or (b) above notify the indemnifying party of the commencement
thereof; but the omission so to notify the indemnifying party will not relieve
it from any liability which it may have to any indemnified party otherwise than
under subsection (a) or (b) above.  In case any such action is brought against
any indemnified party and it notifies an indemnifying party of the commencement
thereof, the indemnifying party will be entitled to participate therein and, to
the extent that it may wish, jointly with any other indemnifying party similarly
notified, to assume the defense thereof, with counsel satisfactory to such
indemnified party (who shall not, except with the consent of the indemnified
party, be counsel to the indemnifying party), and after notice from the
indemnifying party to such indemnified party of its election so to assume the
defense thereof, the indemnifying party will not be liable to such indemnified
party under this Section as the case may be, for any legal or other expenses
subsequently incurred by such indemnified party in connection with the defense
thereof other than reasonable costs of investigation.  No indemnifying party
shall, without the prior written consent of the indemnified party, effect any
settlement of any pending or threatened action in respect of which any
indemnified party is or could have been a party and indemnity could have been
sought hereunder by such indemnified party unless such settlement includes an
unconditional release of such indemnified party from all liability on any claims
that are the subject matter of such action and does not include a statement as
to, or an admission of, fault, culpability or a failure to act by or on behalf
of an indemnified party.

          (d) If the indemnification provided for in this Section  is
unavailable or insufficient to hold harmless an indemnified party under
subsection (a) or (b) above, then each indemnifying party shall contribute to
the amount paid or payable by such indemnified party as a result of the losses,
claims, damages or liabilities referred to in subsection (a) or (b) above (i) in
such proportion as is appropriate to reflect the relative benefits received by
the Company on the one hand and the Underwriters on the other from the offering
of the Offered Securities or (ii) if the allocation provided by clause (i) above
is not permitted by applicable law, in such proportion as is appropriate to
reflect not only the relative benefits referred to in clause (i) above but also
the relative fault of the Company on the one hand and the Underwriters on the
other in connection with the statements or omissions which resulted in such
losses, claims, damages or liabilities as well as any other relevant equitable
considerations.  The relative benefits received by the Company on the one hand
and the Underwriters on the other shall be deemed to be in the same proportion
as the total net proceeds from the offering (before deducting expenses) received
by the Company bear to the total underwriting discounts and commissions received
by the Underwriters.  The relative fault shall be determined by reference to,
among other things, whether the untrue or alleged untrue statement of a material
fact or the omission or alleged omission to state a material fact relates to
information supplied by the Company or the Underwriters and the parties'
relative intent, knowledge, access to information and opportunity to correct or
prevent such untrue statement or omission.  The amount paid by an indemnified
party as a result of the losses, claims, damages or liabilities referred to in
the first sentence of this subsection (d) shall be deemed to include any legal
or other expenses reasonably incurred by such indemnified party in connection
with investigating or defending any action or claim which is the subject of this
subsection (d).  Notwithstanding the provisions of this subsection (d), no
Underwriter shall be required to contribute any amount in excess of the amount
by which the total price at which the Securities underwritten by it and
distributed to the public were offered to the public exceeds the amount of any
damages which such Underwriter has otherwise been required to pay by reason of
such untrue or alleged untrue statement or omission or alleged omission.  No
person guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Act) shall be entitled to contribution from any person who was not
guilty of such fraudulent misrepresentation.  The Underwriters' obligations in
this subsection (d) to contribute are several in proportion to their respective
obligations and not joint.

                                       16
<PAGE>

          (e) The obligations of the Company under this Section shall be in
addition to any liability which the Company may otherwise have and shall extend,
upon the same terms and conditions, to each partner, director and officer of any
Underwriter and to each person, if any, who controls any Underwriter within the
meaning of the Act; and the obligations of the Underwriters under this Section
shall be in addition to any liability which the respective Underwriters may
otherwise have and shall extend, upon the same terms and conditions, to each
director of the Company, to each officer of the Company who has signed a
Registration Statement and to each person, if any, who controls the Company
within the meaning of the Act.

          8.  Default of Underwriters.  If any Underwriter or Underwriters
default in their obligations to purchase Offered Securities hereunder on either
the First or any Optional Closing Date and the aggregate number of shares of
Offered Securities that such defaulting Underwriter or Underwriters agreed but
failed to purchase does not exceed 10% of the total number of shares of Offered
Securities that the Underwriters are obligated to purchase on such Closing Date,
CSFBC may make arrangements satisfactory to the Company for the purchase of such
Offered Securities by other persons, including any of the Underwriters, but if
no such arrangements are made by such Closing Date, the non-defaulting
Underwriters shall be obligated severally, in proportion to their respective
commitments hereunder, to purchase the Offered Securities that such defaulting
Underwriter or Underwriters agreed but failed to purchase on such Closing Date.
If any Underwriter or Underwriters so default and the aggregate number of shares
of Offered Securities with respect to which such default or defaults occur
exceeds 10% of the total number of shares of the Offered Securities that the
Underwriters are obligated to purchase on such Closing Date and arrangements
satisfactory to CSFBC and the Company for the purchase of such Offered
Securities by other persons are not made within 36 hours after such default,
this Agreement will terminate without liability on the part of any non-
defaulting Underwriter or the Company, except as provided in Section 9 (provided
that if such default occurs with respect to Optional Securities after the First
Closing Date, this Agreement will not terminate as to the Firm Securities or any
Optional Securities purchased prior to such termination).  As used in this
Agreement, the term "Underwriter" includes any person substituted for an
Underwriter under this Section.  Nothing herein will relieve a defaulting
Underwriter from liability for its default.

          9. Survival of Certain Representations and Obligations.  The
respective indemnities, agreements, representations, warranties and other
statements of the Company or its officers and of the several Underwriters set
forth in or made pursuant to this Agreement will remain in full force and
effect, regardless of any investigation, or statement as to the results thereof,
made by or on behalf of any Underwriter and the Company or any of their
respective representatives, officers or directors or any controlling person, and
will survive delivery of and payment for the Offered Securities.  If this
Agreement is terminated pursuant to Section 8 or if for any reason the purchase
of the Offered Securities by the Underwriters is not consummated, the Company
shall remain responsible for the expenses to be paid or reimbursed by it
pursuant to Section 5, the respective obligations of the Company and the
Underwriters pursuant to Section 7 shall remain in effect, and if any Offered
Securities have been purchased hereunder the representations and warranties in
Section 2 and all obligations under Section 5, shall also remain in effect.  If
the purchase of the Offered Securities by the Underwriters is not consummated
for any reason other than solely because of the termination of this Agreement
pursuant to Section 8 or the occurrence of any event specified in clause (iii),
(iv) or (v) of Section 6(d), the Company will reimburse the Underwriters for all
out-of-pocket expenses (including fees and disbursements of counsel) reasonably
incurred by them in connection with the offering of the Offered Securities.

          10.  Notices.  All communications hereunder will be in writing and, if
sent to the Underwriters, will be mailed, delivered or telegraphed and confirmed
to the Representatives, c/o Credit Suisse First Boston Corporation, Eleven
Madison Avenue, New York, N.Y. 10010-3629, Attention:  Investment Banking
Department--Transactions Advisory Group; if sent to the Company, will be mailed,
delivered or telegraphed and confirmed to it at 116 Huntington Avenue, Boston,
MA 02116, Attention:  Steven B. Dodge, provided, however, that any notice to an
Underwriter pursuant to Section 7 will be mailed, delivered or telegraphed and
confirmed to such Underwriter.

                                       17
<PAGE>

          11.  Successors.  This Agreement will inure to the benefit of and be
binding upon the parties hereto and their respective personal representatives
and successors and the officers and directors and controlling persons referred
to in Section 7, and no other person will have any right or obligation
hereunder.

          12.  Representation.  The Representatives will act for the several
Underwriters in connection with the transactions contemplated by this Agreement,
and any action under this Agreement taken by the Representatives jointly or by
CSFBC will be binding upon all the Underwriters.

          13.  Counterparts.  This Agreement may be executed in any number of
counterparts, each of which shall be deemed to be an original, but all such
counterparts shall together constitute one and the same Agreement.

          14.  APPLICABLE LAW.  THIS AGREEMENT SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD
TO PRINCIPLES OF CONFLICTS OF LAWS.

          The Company hereby submits to the non-exclusive jurisdiction of the
Federal and state courts in the Borough of Manhattan in The City of New York in
any suit or proceeding arising out of or relating to this Agreement or the
transactions contemplated hereby.

                                       18
<PAGE>

          If the foregoing is in accordance with the Representatives'
understanding of our agreement, kindly sign and return to us three of the
counterparts hereof, whereupon it will become a binding agreement among the
Company and the several Underwriters in accordance with its terms.

                         Very truly yours,

                         American Tower Corporation


                         By:  _________________________________
                              Name:  Steven B. Dodge
                              Title: President and Chief Executive Officer



The foregoing Underwriting Agreement
 is hereby confirmed and accepted
 as of the date first above written.

     Credit Suisse First Boston Corporation,



          Acting on behalf of themselves and as
            the Representatives of the several
            Underwriters.

     By  Credit Suisse First Boston Corporation


     By: _____________________________
         Name:
         Title:

                                       19
<PAGE>

                                   SCHEDULE A


                                            NUMBER OF
                                              FIRM
                                           SECURITIES
                                              TO BE
         UNDERWRITER                        PURCHASED
         -----------                        ---------

Credit Suisse First Boston Corporation







                                            ---------

     Total                                  =========

<PAGE>

                                    ANNEX I


American Towers, Inc.
ATC Merger Corporation
ATC Holding, Inc.
ATC Operating Inc.
ATC GP Inc.
ATC LP, Inc.
American Tower, L.P.
Towersites Monitoring, Inc.
ATC Teleports, Inc.
ATC Realty, Inc.
ATC Financing LLC
ATC Broadcast GP, Inc.
American Tower Delaware Corporation


<PAGE>

                [SULLIVAN & WORCESTER LETTERHEAD APPEARS HERE]

                                                                       EXHIBIT 5



                                January 31 2000



American Tower Corporation
116 Huntington Avenue
Boston, Massachusetts 02116

Ladies and Gentlemen:

     In connection with the registration under the Securities Act of 1933, as
amended (the "Securities Act"), by American Tower Corporation, a Delaware
corporation ("American Tower"), of 11,730,000 shares (the "Shares") of its Class
A Common Stock, par value $.01 per share (the "Class A Common Stock") which
Shares (including those of which may be issued pursuant to the over-allotment
option contained in Registration Statement herein referred to) are to be offered
by American Tower, the following opinion is furnished to you to be filed with
the Securities and Exchange Commission (the "Commission") as Exhibit 5 to
American Tower's registration statement on Form S-3 (the "Registration
Statement").

     We have acted as counsel to American Tower in connection with the
preparation of the Registration Statement, and we have examined originals or
copies, certified or otherwise identified to our satisfaction, of the
Registration Statement, corporate records, certificates and statements of
officers and accountants of American Tower, and of public officials, and such
other documents as we have considered relevant and necessary in order to furnish
the opinion hereinafter set forth.  We express no opinion herein as to any laws
other than the General Corporation Law of the State of Delaware.

     The authorized capital stock of American Tower consists of 20,000,000
shares of preferred stock, par value $.01 per share (the "Preferred Stock"), the
relative designations, preferences, rights and restrictions of which are to be
designated from time to time by the Board of Directors of American Tower,
500,000,000 shares of Class A Common Stock, 50,000,000, shares of Class B Common
Stock, and 10,000,000 shares of Class C Common Stock, par value $.01 per share
(the "Common Stock").

     Based upon and subject to the foregoing, we are of the opinion that: (a)
the Shares have been duly and validly authorized by American Tower; (b) with
respect to the Shares to be offered by American Tower all necessary action on
the part of American Tower in connection therewith have been taken and, upon
delivery to the underwriters against payment therefore in accordance with the
terms of the Underwriting Agreement to be entered into among American Tower,
Credit Suisse First Boston Corporation and the other underwriters named therein,
these Shares will be validly issued, fully paid and nonassessable.
<PAGE>

American Tower Corporation
January 31 2000
Page 2


     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to our firm therein under the
caption "Validity of the Shares."  In giving such consent, we do not thereby
admit that we come within the category of persons whose consent is required
under Section 7 of the Securities Act or under the Rules and Regulations of the
Commission promulgated thereunder.

                                    Very truly yours,

                                    SULLIVAN & WORCESTER LLP








                                      -2-

<PAGE>

                                                                    Exhibit 23.1

                         INDEPENDENT AUDITORS' CONSENT

   We consent to the incorporation by reference in this Registration Statement
of American Tower Corporation on Form S-3 of our report dated March 4, 1999,
appearing in the Annual Report on Form 10-K of American Tower Corporation for
the year ended December 31, 1998 and to the reference to us under the heading
"Experts" in the Prospectus, which is part of this Registration Statement.

/s/ Deloitte & Touche LLP
Boston, Massachusetts
January 31, 2000

<PAGE>

                                                                    Exhibit 23.2

                              Accountants' Consent

The Board of Directors
UNIsite, Inc. and Subsidiaries:

   We consent to the incorporation by reference in the registration statement
on Form S-3 of American Tower Corporation of our report dated March 31, 1999,
with respect to the consolidated balance sheets of UNIsite, Inc. and
Subsidiaries as of December 31, 1998 and 1997, and the related consolidated
statements of operations, redeemable convertible preferred stock and
stockholders' deficit, and cash flows for each of the years in the three-year
period ended December 31, 1998 which report appears in the Form 8-K of American
Tower Corporation dated September 17, 1999.

Tampa, Florida
January 31, 2000                              /s/ KPMG LLP

<PAGE>

                                                                    Exhibit 23.3

                         Independent Auditors' Consent

The Board of Directors
OmniAmerica, Inc. (formerly Specialty Teleconstructors, Inc.):

   We consent to the incorporation by reference in the registration statement
on Form S-3 dated January 31, 2000 of American Tower Corporation of our report
dated August 29, 1997, with respect to the consolidated balance sheet of
OmniAmerica, Inc. and subsidiaries (formerly Specialty Teleconstructors, Inc.)
as of June 30, 1997, and the related consolidated statements of earnings,
stockholders' equity, and cash flows for the year ended June 30, 1997, which
report appears in the Form 8-K of American Tower Corporation dated
September 17, 1999, and to the reference to our firm under the heading
"Experts" in the prospectus.

Albuquerque, New Mexico
January 31, 2000                                 /s/ KPMG LLP

<PAGE>

                                                                    Exhibit 23.4

                        Consent of Independent Auditors

   We consent to the reference to our firm under the caption "Experts" in the
Registration Statement on Form S-3 and related Prospectus of American Tower
Corporation expected to be filed on or about January 31, 2000 for the
registration of shares of its Class A common stock and to the incorporation by
reference therein of our report dated September 16, 1998, with respect to the
consolidated financial statements of OmniAmerica, Inc. and Subsidiaries
(formerly Specialty Teleconstructors, Inc.) at and for the year ended June 30,
1998, included in American Tower Corporation's Form 8-K.

Dallas, Texas
January 31, 2000                        /s/ Ernst & Young LLP

<PAGE>

                                                                    Exhibit 23.5

                        Consent of Independent Auditors

   We consent to the reference to our firm under the caption "Experts" in the
Registration Statement on (Form S-3 No. 333-00000) of American Tower
Corporation and incorporation by reference of our reports dated April 1, 1999
with respect to the financial statements of TeleCom Towers, LLC as of December
31, 1998 and 1997 and for the year ended December 31, 1998 and the period from
September 30, 1997 (inception) to December 31, 1997 and the financial
statements of TeleCom Towers Mid-Atlantic, LP, TeleCom Towers of the West, LP
and TeleCom Southwest Towers, LP as of July 31, 1998 and December 31, 1997 and
for the seven months ended July 31, 1998 and the year ended December 31, 1997,
included in the Form 8-K of American Tower Corporation dated September 17,
1999, filed with the Securities and Exchange Commission.

McLean, Virginia
January 31, 2000                        /s/ Ernst & Young LLP

<PAGE>

                                                                    Exhibit 23.6

                              ACCOUNTANTS' CONSENT

The Board of Directors and Stockholder
RCC Consultants, Inc.:

   We consent to the use of our reports, dated February 24, 1999 incorporated
herein by reference and to the reference to our firm under the heading
"Experts" in the prospectus.

Short Hills, New Jersey
January 28, 2000                                 /s/ KPMG LLP

<PAGE>

                                                                  Exhibit 23.7

                   CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

   As independent public accountants, we hereby consent to the incorporation by
reference in this registration statement on Form S-3 of American Tower
Corporation of our report dated November 25, 1998 included in Wauka
Communications, Inc.'s financial statements for the period ended October 26,
1998 and to all references of our Firm included in or made a part of this
registration statement.

Atlanta, Georgia
January 31, 2000                      /s/ Arthur Andersen LLP

<PAGE>

                                                                    Exhibit 23.8

                        CONSENT OF INDEPENDENT AUDITORS
The Board of Directors
American Tower Corporation

   We consent to the incorporation by reference in the registration statement
on Form S-3 of American Tower Corporation dated January 31, 2000 of our report
dated January 23, 1998, with respect to the consolidated financial statements
of American Tower Corporation and subsidiaries (old ATC) as of December 31,
1997 and 1996, and for each of the years in the three year period ended
December 31, 1997, which report appears in the Form 8-K of American Tower
Corporation dated September 17, 1999, and to the reference to our firm under
the heading "Experts" in the prospectus.

Houston, Texas
January 31, 2000                                 /s/ KPMG LLP


© 2022 IncJournal is not affiliated with or endorsed by the U.S. Securities and Exchange Commission