X0306 4 2014-03-10 0001053507 AMERICAN TOWER CORP /MA/ AMT 0001218672 TAICLET JAMES D JR 116 HUNTINGTON AVENUE BOSTON MA 02116 1 1 0 0 Chairman, President and CEO Common Stock 2014-03-10 4 M 0 11888 0 A 11888 D Common Stock 2014-03-10 4 F 0 5606 81.18 D 6282 D Common Stock 2014-03-10 4 M 0 14770 0 A 21052 D Common Stock 2014-03-10 4 F 0 6965 81.18 D 14087 D Common Stock 2014-03-11 4 M 0 14630 0 A 28717 D Common Stock 2014-03-11 4 F 0 6794 81.70 D 21923 D Common Stock 1630 I By minor children Common Stock 100041 I By GRAT Restricted Stock Units 2014-03-10 4 M 0 11888 0 D Common Stock 11888 0 D Restricted Stock Units 2014-03-10 4 M 0 14770 0 D Common Stock 14770 14769 D Restricted Stock Units 2014-03-11 4 M 0 14630 0 D Common Stock 14630 43888 D Option to Purchase Common Stock 81.18 2014-03-10 4 A 0 303235 0 A 2024-03-10 Common Stock 303235 303235 D Restricted Stock Units 2014-03-10 4 A 0 55433 0 A Common Stock 55433 55433 D The reporting person disclaims beneficial ownership in shares owned by minor children. 100,041 shares were previously reported as directly beneficially owned. These shares were contributed to a grantor retained annuity trust ("GRAT") on December 20, 2013. Each Restricted Stock Unit (RSU) respresents a contingent right to receive one share of Common Stock. This RSU was granted on March 10, 2010 pursuant to the 2007 Equity Incentive Plan, and vests in 25% cumulative annual increments beginning March 10, 2011. This Form 4 reflects the vesting of this RSU on March 10, 2014 as to 100% of the original grant amount. This RSU was granted on March 10, 2011 pursuant to the 2007 Equity Incentive Plan, and vests in 25% cumulative annual increments beginning March 10, 2012. This Form 4 reflects the vesting of this RSU on March 10, 2014 as to 75% of the original grant amount. This RSU was granted on March 11, 2013 pursuant to the 2007 Equity Incentive Plan, and vests in 25% cumulative annual increments beginning March 11, 2014. This Form 4 reflects the vesting of this RSU on March 11, 2014 as to 25% of the original grant amount. This option was granted on March 10, 2014 pursuant to the 2007 Equity Incentive Plan and is exercisable in 25% cumulative annual increments beginning March 10, 2015. This RSU was granted on March 10, 2014 pursuant to the 2007 Equity Incentive Plan and vests in 25% cumulative annual increments beginning March 10, 2015. /s/ Mneesha O. Nahata, as attorney-in-fact 2014-03-12