**Exhibit 31.1**

 

**CERTIFICATIONOF CHIEF EXECUTIVE OFFICER**

**Section 302Certification**

 

I, Anthony R. Fabiano, certify that:

 
| 1.     |   | I have reviewed this quarterly report on Form 10-Q  of American Science and Engineering, Inc.;                                                                                                                                                                                                                                                                                                                            |
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| 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;                                                                                                                      |
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| 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;                                                                                                                                         |
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| 4.     |   | The registrant’s other certifying officer  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))  and internal control over financial reporting (as defined in Exchange Act rules 13a-15(f) and  15d-15(f)) for the registrant and have:                                                                   |
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|   |   | 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)        Designed such internal  control over financial reporting, or caused such internal control over  financial reporting to be designed under our supervision, to provide  reasonable assurance regarding the reliability of financial reporting and the  preparation of financial statements for external purposes in accordance with  generally accepted accounting principles;           |
|   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                |
|   |   | c)         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; and                                                                                      |
|   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                |
|   |   | d)        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;                                                          |
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| 5.     |   | The registrant’s other certifying officer  and I have disclosed, based on our most recent evaluation of internal control  over financial reporting, to the registrant’s auditors and the audit  committee of the registrant’s board of directors (or persons performing the  equivalent functions):                                                                                                                  |
|   |   |                                                                                                                                                                                                                                                                                                                                                                                                                                |
|   |   | 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                                                                                               |
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|   |   | 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: February 9, 2006           |   |
|---------------------------------------|--------|
|                                  |   |
| /s/ Anthony R. Fabiano                |   |   |
| Anthony R. Fabiano                    |   |
| President and Chief Executive Officer |   |
|                                       |        |  |

 

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