***Exhibit 31.1***

* *

CERTIFICATION OF CHIEF EXECUTIVEOFFICER

Section 302 Certification

 

I, Anthony R. Fabiano, certify that:

 
| 1.     | I have reviewed this quarterly report on Form 10-Q of American  Science and Engineering, Inc.;                                                                                                                                                                                                                 |
|--------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |                                                                                                                                                                                                                                                                                                           |   |
| 2.     | Based on my knowledge, this report does not contain any untrue  statement of a material fact or omit to state a material fact necessary to  make the statements made, in light of the circumstances under which such  statements were made, not misleading with respect to the period covered by  this report; |
|   |                                                                                                                                                                                                                                                                                                           |   |
| 3.     | Based on my knowledge, the financial statements, and other financial  information included in this report, fairly present in all material respects  the financial condition, results of operations and cash flows of the  registrant as of, and for, the periods presented in this report;                     |
|   |                                                                                                                                                                                                                                                                                                           |
| 4.     | The registrant’s other certifying officers and I are responsible for  establishing and maintaining disclosure controls and procedures (as defined  in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:                                                                            |
|   |                                                                                                                                                                                                                                                                                                           |   |
|   | a)                                                                                                                                                                                                                                                                                                             | Designed such disclosure controls and procedures, or caused such  disclosure controls and procedures to be designed under our supervision to  ensure that material information relating to the registrant, including its  consolidated subsidiary, is made known to us by others within those entities,  particularly during the period in which this report is being prepared; |
|   |                                                                                                                                                                                                                                                                                                           |   |
|   | b)                                                                                                                                                                                                                                                                                                             | Evaluated the effectiveness of the registrant’s disclosure controls  and procedures and presented in this report our conclusions about the  effectiveness of the disclosure controls and procedures as of the end of the  period covered by this report based on such evaluation; |
|   |                                                                                                                                                                                                                                                                                                           |   |
|   | c)                                                                                                                                                                                                                                                                                                             | Disclosed in this report any change in the registrant’s internal  control over financial reporting that occurred during the registrant’s most  recent fiscal quarter that has materially affected, or is reasonably likely  to materially affect, the registrant’s internal control over financial  reporting; |
|   |                                                                                                                                                                                                                                                                                                           |   |
| 5.     | The registrant’s other certifying officers and I have disclosed,  based on our most recent evaluation, to the registrant’s auditors and the  audit committee of the registrant’s board of directors (or persons performing  the equivalent function):                                           |
|   |                                                                                                                                                                                                                                                                                                           |   |
|   | a)                                                                                                                                                                                                                                                                                                             | All significant deficiencies and material weaknesses in the design or  operation of internal control over financial reporting which are reasonable  likely to adversely affect the registrant’s ability to record, process,  summarize and report financial information; and |
|   |                                                                                                                                                                                                                                                                                                           |   |
|   | b)                                                                                                                                                                                                                                                                                                             | Any fraud, whether or not material, that involves management or other  employees who have a significant role in the registrant’s internal control  over financial reporting. |
|        |                                                                                                                                                                                                                                                                                                                |  |  |

 

 
| Date: November 3, 2004                |
|---------------------------------------|
|                                  |
| /s/ Anthony R. Fabiano                |   |
| Anthony R. Fabiano                    |
| President and Chief Executive Officer |

 

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