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                                                           Exhibit (10)(b)(xvii)


                              EMPLOYMENT AGREEMENT


This Agreement is made as of July 10, 1998 by and between American Science and
Engineering, Inc. (the "Company"), a Massachusetts corporation having its
principal place of business in Billerica, Massachusetts, and Lee C. Steele, of
Boston, Massachusetts (the "Executive").

The Company desires to retain the services of the Executive, and the Executive
is willing to render such services, in accordance with the terms hereinafter set
forth.

Accordingly, the Company and the Executive agree as follows:

1.   The Company agrees to continue the employment of the Executive as, and the
Executive agrees to continue to perform the duties of, Vice President, Finance
and Chief Financial Officer of the Company.

2.   (a) The Company shall pay to the Executive the "Severance Payment" in the
event that the Executive is terminated by the Company within sixty (60) days
prior to or twelve (12) months after the occurrence of a "Change of Control," as
defined below. The Severance Payment shall be made at the time of such
termination.

     (b) The "Severance Payment" shall be a one-time payment equal to the higher
of: (i) the annual rate of the Executive's base salary in effect one month prior
to the occurrence of the Change of Control, or (ii) the annual rate of the
Executive's base salary in effect at the time of such termination. The Severance
Payment shall also include the continuation of all benefits received by the
Executive prior to termination for a period equal to the lesser of one year or
the start of new employment by the Executive in which he receives substantially
similar benefits.

     (c) A "Change of Control" shall be deemed to have occurred if:

     (i) any person (as defined in Section 13(d) or 14(d)(2) of the Securities
     Exchange Act of 1934) shall have become the beneficial owner of 50 percent
     or more of the combined voting power of the Company's voting securities;

     (ii) the Continuing Directors shall have ceased for any reason to
     constitute a majority of the Board of Directors of the Company. For this
     purpose, a "Continuing Director" shall include member of the Board of
     Directors of the Company as of the date of this Agreement and any person
     nominated for election to the Board of Directors of the Company by a vote
     of the majority of the then Continuing Directors;

     (iii) the stockholders approve the complete liquidation or dissolution of
     the Company, or

     (iv) the stockholders approve by the requisite vote any of the following
     transactions: (A) a merger or consolidation of the Company (except for a
     merger in respect of which no vote of the stockholders of the Company is
     required); (B) a sale, lease, exchange, mortgage, pledge, transfer or other
     disposition (in one transaction or a series of transactions), whether as
     part of a dissolution or otherwise, of assets of the Company or of any
     direct or indirect majority-owned subsidiary or the Company (other than to


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     any direct or indirect wholly-owned subsidiary or to the Company) having an
     aggregate market value equal to 50% or more of either the aggregate market
     value of all of the assets of the Company determined on a consolidated
     basis or the aggregate market value of all the outstanding stock of the
     Company immediately prior to the transaction; or (C) a tender or exchange
     offer for 50% or more of the outstanding voting stock of the Company.

3.   (a) If the Executive is terminated for any reason other than (i) Cause (as
defined below); or (ii) pursuant to Paragraph 2 ("Termination for Convenience")
the Executive shall receive an amount equal to the greater of the amount that
would be due under the Company's then-current severance policy, if any, or six
months of his then-current Base Pay, payable at the Company's option, on the
last date of his employment or in weekly installments. In case of Termination
for Convenience, the Executive shall be entitled to a continuation of all
benefits being received by him at the time of termination for the lesser of six
(6) months from the date of termination, or until the date in which the
Executive begins new employment in which he receives substantially similar
benefits. If the Executive is Terminated for Convenience within twelve (12)
months of a change in the Company's President/CEO, the Executive shall be
entitled to receive the Severance Payment described in Paragraph 2(b) in place
of the benefits described in this Paragraph 3.

     (b) For the purposes of this Agreement, "Cause" shall mean: (i) the
determination by the President of the Company, in agreement with the Board of
Directors, that the Executive has willfully failed to perform his duties in the
course of his employment under this Agreement consistent with those of a Vice
President of Finance and Chief Financial Officer as expressly instructed by the
President/CEO; or (ii) the final conviction of the Executive for, or his plea of
nolo contendere to, a felony or any other crime which involves fraud, dishonesty
or moral turpitude.

4.   The Company may not assign all or any part of its obligations under this
Agreement except to a successor as provided for in this paragraph. The Company
will require any successor (whether direct or indirect, by purchase, merger,
consolidation or otherwise) to all or substantially all of the business or
assets of the Company expressly to assume and agree to perform this Agreement to
the same extent that the Company would be required to perform it if no
succession had taken place. As used in this Agreement, unless the context
requires otherwise, the "Company" shall mean the Company as defined above or any
successor to its business or assets as aforesaid which assumes and agrees to
perform this Agreement, by operation of law, or otherwise. This Agreement shall
inure to the benefit of and be enforceable by and binding upon (i) any such
successor and (ii) the Executive's personal or legal representatives, executors,
administrators and designated beneficiaries.

5.   This Agreement contains the entire agreement between the parties with 
respect to the subject matter hereof and supersedes all prior oral and written
agreements, understandings and commitments between the parties relating to this
Agreement. Notwithstanding the foregoing, the Executive shall at all times
remain subject to all policies and procedures of the Company that relate to
employees of the Company, except to the extent that this Agreement contains
terms or provisions that are contrary to or provides greater benefits than such
policies and procedures, in


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which case this Agreement shall control. No amendment to this Agreement shall be
made except by a written instrument signed by both parties.

6.   This Agreement shall be construed and enforced under and be governed in all
respects by the law of The Commonwealth of Massachusetts, without regard to the
conflict of law principles thereof.

IN WITNESS WHEREOF, the Company has caused this instrument to be executed on its
behalf by a duly authorized officer and the Executive has executed this
instrument, all as of the date set forth above.


          AMERICAN SCIENCE AND ENGINEERING, INC.



          By: 
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                  Ralph S. Sheridan, President



               ------------------------------------
                  Lee C. Steele



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