AMERICAN TOWER CORP /MA/ — Director's Dealing 2011

Mar 21, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: AMERICAN TOWER CORP /MA/ (AMT)
CIK: 0001053507
Period of Report: 2011-03-17

Reporting Person: HESS WILLIAM H (EVP, Int'l. Operations)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-03-17	Class A Common Stock	M	6250	—	Acquired	17848	Direct
2011-03-17	Class A Common Stock	F	2610	$51.04	Disposed	15238	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-03-17	Restricted Stock Units	$	M	6250	Disposed		Class A Common Stock (6250)	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Class A Common Stock	3662	Indirect

Footnotes

F1: Each Restricted Stock Unit (RSU) respresents a contingent right to receive one share of Class A Common Stock.

F2: This RSU was granted on March 17, 2008 pursuant to the 2007 Equity Incentive Plan, and vests in 25% cumulative annual increments beginning March 17, 2009. This Form 4 reflects the vesting of this RSU on March 17, 2011 as to 75% of the original grant amount.