**Exhibit31.1**

 

**CERTIFICATIONOF CHIEF EXECUTIVE OFFICER**

**Section 302Certification**

 

I, Anthony R. Fabiano, certify that:

 

1.                                       Ihave reviewed this report on Form 10-K/A of American Science andEngineering, Inc.;

 

2.                                       Based on my knowledge, this report does not containany untrue statement of a material fact or omit to state a material factnecessary to make the statements made, in light of the circumstances underwhich such statements were made, not misleading with respect to the periodcovered by this report;

 

3.                                       Basedon my knowledge, the financial statements, and other financial informationincluded in this report, fairly present in all material respects the financialcondition, results of operations and cash flows of the registrant as of, andfor, the periods presented in this report;

 

4.                                       Theregistrant’s other certifying officer(s) and I are responsible for establishingand maintaining disclosure controls and procedures (as defined in Exchange ActRules 13a-15(e) and 15d-15(e)) for the registrant and have:

 

a)                                      Designed such disclosure controls and procedures, orcaused such disclosure controls and procedures to be designed under oursupervision, to ensure that material information relating to the registrant,including its consolidated subsidiary, is made known to us by others withinthose entities, particularly during the period in which this report is beingprepared;

 

b)                                     Evaluated theeffectiveness of the registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by thisreport based on such evaluation; and

 

c)                                      Disclosed in thisreport any change in the registrant’s internal control over financial reportingthat occurred during the registrant’s fourth fiscal quarter that has materially affected, or is reasonablylikely to materially affect, the registrant’s internal control over financialreporting; and

 

5.                                       Theregistrant’s other certifying officers and I have disclosed, based on our mostrecent evaluation of internal control over financial reporting, to theregistrant’s auditors and the audit committee of registrant’s board ofdirectors (or persons performing the equivalent functions):

 

a)                                      All significantdeficiencies and material weaknesses in the design or operation of internalcontrol over financial reporting which are reasonable likely to adverselyaffect the registrant’s ability to record, process, summarize and reportfinancial information; and

 

b)                                     Any fraud, whetheror not material, that involves management or other employees who have asignificant role in the registrant’s internal control over financial reporting.

 

 
| Date: **February  15, 2005** | /s/ ANTHONY R. FABIANO                  |   |
|------------------------------|-----------------------------------------|--------|
|                         | Anthony R. Fabiano                      |
|                         | *President and Chief Executive Officer* |

 

----