X0303 4 2011-05-10 0000005768 AMERICAN SCIENCE & ENGINEERING, INC. ASEI 0001447577 Cline Robert B AMERICAN SCIENCE AND ENGINEERING, INC. 829 MIDDLESEX TURNPIKE BILLERICA MA 01821 0 1 0 0 SVP Common Stock 2011-05-10 4 S 0 757 85.82 D 6943 D Common Stock 2011-05-10 4 S 0 303 86.10 D 6640 D On June 12, 2008, the reporting person was granted a restricted stock award for 1886 shares of common stock. The award vests based on satisfaction of certain performance criteria within a five year period from date of grant. The performance criteria was met for all of the shares, resulting in vesting of the award as to 1886 shares. On May 15, 2009, the reporting person was granted a restricted stock award for 3599 shares of common stock. The award vests based on satisfaction of certain performance criteria within a five year period from date of grant. The performance criteria was met as to two thirds of the shares, resulting in vesting of the award as to 2399 shares. The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 9, 2011. The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from a low of $84.63 to a high of $86.39 for an average of $85.82. The reporting person undertakes to provide to American Science and Engineering, Inc., any security holder of American Science and Engineering, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote to this Form 4. /s/ M. Colette Cooke 2011-05-11