**Exhibit 31.1**

**CERTIFICATIONOF CHIEF EXECUTIVE OFFICERSection 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 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:                                          |
|   |   |                                                                                                                                                                                                                                                                                                                                                                                                        |
|   |   | 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;                                                    |
|   |   |                                                                                                                                                                                                                                                                                                                                                                                                        |
| 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                                                                                               |
|   |   |                                                                                                                                                                                                                                                                                                                                                                                                        |
|   |   | 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, 2007                |   |
|---------------------------------------|--------|
|                                  |   |
| /s/ Anthony R. Fabiano                |   |
| Anthony R. Fabiano                    |   |
| President and Chief Executive Officer |   |

 

 

----