X0303 4 2011-05-13 0000005768 AMERICAN SCIENCE & ENGINEERING, INC. ASEI 0001353373 Breur Kenneth AMERICAN SCIENCE AND ENGINEERING, INC. 829 MIDDLESEX TURNPIKE BILLERICA MA 01821 0 1 0 0 SVP Common Stock 2011-05-13 4 S 0 1859 88.54 D 3110 D Common Stock 2011-05-13 4 M 0 235 51.56 A 3345 D Common Stock 2011-05-13 4 S 0 235 88.00 D 3110 D Common Stock 2011-05-13 4 M 0 801 61.40 A 3911 D Common Stock 2011-05-13 4 S 0 801 88.00 D 3110 D Stock Option (right to buy) 51.56 2011-05-13 4 M 0 235 0 D 2011-05-06 2018-06-12 Common Stock 235 0 D Stock Option (right to buy) 61.40 2011-05-13 4 M 0 801 0 D 2011-05-06 2019-05-15 Common Stock 801 401 D The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from a low of $88.51 to a high of $88.55 for an average of $88.54. 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. On June 12, 2008, the reporting person was granted an option to purchase 704 shares of common stock. The option vests in increments based on AS&E's satisfaction of certain performance criteria. The performance criteria was met for one third of the goals, resulting in vesting of the option as to 235 shares. On May 15, 2009, the reporting person was granted an option to purchase 1202 shares of common stock. The option vests in increments based on AS&E's satisfaction of certain performance criteria. The performance criteria was met for two thirds of the goals, resulting in vesting of the option as to 801 shares. /s/ Colette Cooke, attorney-in-fact 2011-05-16