**Exhibit31.1**

**CERTIFICATIONOF CHIEF EXECUTIVE OFFICER**

**Section302 Certification**

I, Anthony R.Fabiano, certify that:

1.     I have reviewed this reporton Form 10-K 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 tostate a material fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading withrespect to the period covered by this report;

3.               Based on myknowledge, the financial statements, and other financial information includedin 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.               The registrant’sother certifying officer and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e)and 15d-15(e)) and internal control over financial reporting (as defined inExchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a)              Designed suchdisclosure controls and procedures, or caused such disclosure controls andprocedures to be designed under our supervision, to ensure that materialinformation relating to the registrant, including its consolidated subsidiary,is made known to us by others within those entities, particularly during theperiod in which this report is being prepared;

b)             Designed suchinternal control over financial reporting, or caused such internal control overfinancial reporting to be designed under our supervision, to provide reasonableassurance regarding the reliability of financial reporting and the preparationof financial statements for external purposes in accordance with generallyaccepted accounting principles;

c)              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

d)             Disclosed in thisreport any change in the registrant’s internal control over financial reportingthat occurred during the registrant’s fourth fiscal quarter that has materiallyaffected, or is reasonably likely to materially affect, the registrant’sinternal control over financial reporting; and

5.               The registrant’sother certifying officer and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to the registrant’sauditors and the audit committee of the registrant’s board of directors (orpersons performing the equivalent functions):

a)              All significantdeficiencies and material weaknesses in the design or operation of internal controlover financial reporting which are reasonable likely to adversely affect theregistrant’s ability to record, process, summarize and report financialinformation; and

b)             Any fraud, whether ornot material, that involves management or other employees who have asignificant role in the registrant’s internal control over financial reporting.
| Date: June 12, 2007 |
|---------------------|
|                | /s/ ANTHONY R. FABIANO |   |
|                | Anthony R. Fabiano |   |
| * *            | *President and Chief Executive Officer* | * * |

 

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