AMERICAN TOWER CORP /MA/ — Director's Dealing 2010

Oct 8, 2010

SEC Form 3 — Initial Statement of Beneficial Ownership

Issuer: AMERICAN TOWER CORP /MA/ (AMT)
CIK: 0001053507
Period of Report: 2010-09-30

Reporting Person: Kearns Mark (VP Finance and Treasurer)

Holdings (Derivative)

Security	Exercise Price	Expiration	Underlying	Shares	Ownership
Option to purchase Class A Common Stock	$39.84	2020-06-01	Class A Common Stock (13667)		Direct
Restricted Stock Units	$		Class A Common Stock (4707)		Direct

Footnotes

F1: This option was granted pursuant to the 2007 Equity Incentive Plan and is exercisable in 25% cumulative annual increments beginning June 1, 2011.

F2: This Restricted Stock Unit (RSU) was granted pursuant to the 2007 Equity Incentive Plan and vests in 25% cumulative annual increments beginning June 1, 2011.

F3: Each RSU represents a contingent right to receive one share of Class A Common Stock.