<PAGE>

    AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JANUARY 17, 2001.
                                                           REGISTRATION NO. 333-
================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                     ---------------------------------------


                     AMERICAN SCIENCE AND ENGINEERING, INC.
             ------------------------------------------------------
             (Exact Name of Registrant as Specified in Its Charter)


          MASSACHUSETTS                                         04-2440991
---------------------------------                          ---------------------
(State or Other Jurisdiction of                              (I.R.S. Employer
 Incorporation or Organization                              Identification No.)


                   829 MIDDLESEX TURNPIKE, BILLERICA, MA        01821
            ------------------------------------------------------------
               (Address of Principal Executive Offices)       (Zip Code)

                                 ---------------

                     AMERICAN SCIENCE AND ENGINEERING, INC.
                       2000 COMBINATION STOCK OPTION PLAN
                       ----------------------------------
                            (Full Title of the Plan)

                            STEVEN R. LONDON, ESQUIRE
                         BROWN, RUDNICK, FREED & GESMER
                              ONE FINANCIAL CENTER
                          BOSTON, MASSACHUSETTS 02111
                     ---------------------------------------
                     (Name and Address of Agent for Service)

                                 (617) 856-8200
                      -------------------------------------
          (Telephone Number, Including Area Code, of Agent for Service)

                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>
=================================================================================================================
                                                        Proposed            Proposed
                                      Amount             Maximum       Maximum Aggregate
    Title of Each Class of            to be          Offering Price    Offering Price (1)        Amount of
 Securities to be Registered        Registered        Per Share (1)                          Registration Fee
-----------------------------------------------------------------------------------------------------------------
<S>                                <C>                <C>                <C>                        <C>
Common Stock,                      440,000 (2)        $4.53125 (3)       $1,993,750 (3)             $498.44
$.66 2/3 par value

Rights to Purchase                 440,000                 0   (5)                0 (5)                   0(5)
Common Stock (4)
=================================================================================================================
</TABLE>

     (1) Estimated solely for the purpose of determining the registration fee
pursuant to Rule 457(h) under the Securities Act of 1933, as amended.

     (2) Such presently indeterminable number of additional shares of Common
Stock are also registered hereunder as may be issued in the event of a merger,
consolidation, reorganization, recapitalization, stock dividend, stock split,
stock combination or other similar change in Common Stock.

<PAGE>

     (3) Based upon the average high and low prices for the Registrant's Common
Stock, $.66 2/3 par value (the "Common Stock"), on January 11, 2001 as reported
by the American Stock Exchange.

     (4) Pursuant to a Rights Agreement entered into in 1998, one right (each a
"Right") is deemed to be delivered with each outstanding share of Common Stock.
The 440,000 Rights registered hereby consist of 440,000 Rights which may be
issued with shares of Common Stock issuable upon exercise of options granted or
to be granted under the Registrant's 2000 Combination Stock Option Plan.

     (5) The Rights are not separately transferable apart from the Common Stock,
nor are they exercisable until the occurrence of certain events. Accordingly, no
independent value has been attributed to the Rights.

<PAGE>

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         The following documents are hereby incorporated by reference into this
Registration Statement:

         (a)      The Registrant's latest Annual Report on Form 10-K for the
                  fiscal year ended March 31, 2000 filed pursuant to Section
                  13(a) or 15(d) of the Securities Exchange Act of 1934, as
                  amended (the "Exchange Act");

         (b)      All other reports filed by the Registrant pursuant to Section
                  13(a) or 15(d) of the Exchange Act since the end of the fiscal
                  year covered by the Registrant's annual report referred to in
                  (a) above; and

         (c)      The description of the Registrant's Common Stock contained in
                  the Registrant's Registration Statement on Form 8-A (File No.
                  001-06549) pursuant to the Exchange Act with the Securities
                  and Exchange Commission (the "Commission"), and the
                  description of the Rights contained in the Registrant's
                  Registration Statement on Form 8-A, filed on April 15, 1998,
                  with the Commission, and all amendments thereto and reports
                  filed for the purpose of updating such descriptions.

         All documents filed by the Registrant pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Exchange Act, subsequent to the date hereof and
prior to the filing of a post-effective amendment which indicates that all
securities offered have been sold or which deregisters all securities then
remaining unsold, shall be deemed hereby incorporated by reference in this
Registration Statement and to be a part hereof from the date of filing of
such documents. Any statement contained in a document incorporated or deemed
to be incorporated by reference herein shall be deemed to be modified or
superseded for purposes of this registration statement to the extent that a
statement contained herein or in any subsequently filed document which also
is or is deemed to be incorporated by reference herein modifies or supersedes
such statement.

Item 4.  DESCRIPTION OF SECURITIES.

         Not Applicable.

Item 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

         The validity of the shares of Common Stock to be issued in accordance
with the American Science and Engineering, Inc. 2000 Combination Stock Option
Plan has been passed upon for the Registrant by Brown, Rudnick, Freed & Gesmer,
One Financial Center, Boston, Massachusetts 02111.

Item 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

        Section 67 of Chapter 156B of the Massachusetts General Laws permits the
indemnification of directors and officers to the extent authorized by the
Articles of Organization or By-Laws of a corporation or by a vote of the
stockholders. Except as otherwise provided by the Articles of Organization or
By-Laws, indemnification of persons who are not directors of a corporation may
be provided to the extent authorized by the directors. No indemnification may be
provided for any person with respect to any matter as to which he shall have
been adjudicated in any proceeding not to have acted in good faith in the
reasonable belief that his action was in the best interest of the corporation.

        Article VI of the Registrant's By-Laws provides, in substance, that the
Registrant shall indemnify any person who was or is a party or is threatened to
be made a party to any threatened, pending or completed action or suit, by

                                      II-1
<PAGE>

reason of the fact that he is or was serving as a director or officer of the
Registrant or is or was serving at the request of the Registrant as a director,
trustee or officer of another corporation or entity. The indemnification
provisions apply to expenses actually incurred by such person in connection with
any civil action, suit or proceeding to which such person may be made a party,
or by which such person shall be threatened, by reason of any alleged act or
failure to act in his present or former capacity as a director or officer of the
Registrant or as a director, trustee or officer of such affiliated corporation
or entity. No person, however, has the right to indemnification in relation to
any matter as to which such person shall have been finally adjudged in any legal
proceeding not to have acted in good faith and the reasonable belief that the
person's action was in the best interest of the Registrant. In the event of any
settlement of any action, suit or proceeding, the right to indemnification is
limited to matters as to which the Registrant is advised by counsel that such
settlement is reasonable and that such person has acted in good faith and the
reasonable belief that his action was in the best interest of the Registrant.
The right of indemnification contained in the Registrant's By-Laws is
non-exclusive and is in addition to any other rights such person may have.

         The Registrant has also entered into indemnification agreements with
all of its directors and executive officers (the "Indemnitees"). In general,
these agreements provide that the Registrant will indemnify and advance expenses
to the Indemnitees to the fullest extent permitted by law. More specifically,
the Registrant must indemnify the Indemnitees if, by reason of the Indemnitee's
corporate status, the Indemnitee is, or is threatened to be made, a party to or
is otherwise involved in any legal proceeding brought by: (1) persons other than
the Registrant; or (2) or in the right of the Registrant. The Indemnitee will
only be indemnified, however, if the Indemnitee acted in good faith and is
adjudged not to have received an improper personal benefit. In a claim brought
by or on behalf of the Registrant, no indemnification will be made if the
Indemnitee is adjudged to be liable to the Registrant unless a court deciding
the matter decides otherwise. Finally, notwithstanding the foregoing discussion,
if an Indemnitee is successful on the merits of a proceeding, the Indemnitee
will be indemnified to the maximum extent permitted by law from all expenses,
judgments, penalties, fines and amounts paid in settlement, actually and
reasonably incurred.

Item 7.  EXEMPTION FROM REGISTRATION CLAIMED.

         Not Applicable.

                                      II-2
<PAGE>

Item 8.  EXHIBITS.

<TABLE>
<CAPTION>
NUMBER EXHIBIT    DESCRIPTION OF EXHIBIT                                                   PAGE
<S>               <C>                                                                      <C>
4.1               Restated Articles of Organization of the Registrant, as
                  amended by: (a) Articles of Amendment dated October 29, 1976;
                  (b) Articles of Amendment dated May 17, 1976; (c) Articles of
                  Amendment dated March 28, 1973; (d) Articles of Amendment
                  dated November 5, 1996 (each of the foregoing is filed as
                  Exhibit 4.1 to the Registrant's Registration Statement on Form
                  S-8 filed on May 28, 1997 (Reg. No. 333-27929) with respect to
                  the Registrant's Executive Equity Incentive Plan); and (e)
                  Certificate of Vote of Directors Establishing a Class or
                  Series of Stock dated April 14, 1998 (filed as Exhibit 4.1 to
                  the Registrant's Registration Statement on Form S-8 filed on
                  December 24, 1998 (Reg. No. 333-69717) with respect to the
                  Registrant's 1998 Non-Qualified Stock Option Plan).                         *

4.2               By-Laws of the Registrant, as amended (filed as Exhibit
                  2(a)(iii) to Registrant's Registration Statement on Form S-7,
                  Registration No. 2-56452 (the "Form S-7")).                                 *

4.3               Specimen Certificate of Common Stock (filed as Exhibit 2(a)(i)
                  to the Form S-7).                                                           *

4.4               Shareholder Rights Agreement (the "Rights Agreement") dated as
                  of April 17, 1998 between Registrant and American Stock
                  Transfer & Trust Co., Inc., as Rights Agent (filed as Exhibit
                  4 to the Current Report on Form 8-K filed on April 15, 1998).               *

5.1               Legal Opinion of Brown, Rudnick, Freed & Gesmer.                           11

23.1              Consent of Brown, Rudnick, Freed & Gesmer.                                 **

23.2              Consent of Arthur Andersen LLP.                                            15

24                Power of Attorney.                                                        ***

99                American Science and Engineering, Inc. 2000 Combination Stock
                  Option Plan. (filed as Exhibit A to the Definitive Proxy
                  Statement on Schedule 14A filed on August 18, 2000).                        *
</TABLE>

---------------------------------------------------
*        Not filed herewith. In accordance with Rule 411(c) promulgated pursuant
         to the Securities Act of 1933, as amended, reference is made to the
         documents previously filed with the Securities and Exchange Commission
         which documents are hereby incorporated by reference.
**       Contained in Exhibit 5.
***      Included on Signature Page of this Registration Statement.

                                      II-3
<PAGE>

Item 9.  UNDERTAKINGS.

         (a)      The undersigned Registrant hereby undertakes:

                  (1)      To file, during any period in which offers or sales
                           are being made, a post-effective amendment to this
                           Registration Statement to include any material
                           information with respect to the plan of distribution
                           not previously disclosed in the Registration
                           Statement or any material change to such information
                           in the Registration Statement.

                  (2)      That, for the purpose of determining any liability
                           under the Securities Act of 1933, each such
                           post-effective amendment shall be deemed to be a new
                           registration statement relating to the securities
                           offered therein, and the offering of such securities
                           at that time shall be deemed to be the initial BONA
                           FIDE offering thereof.

                  (3)      To remove from registration by means of a
                           post-effective amendment any of the securities being
                           registered which remain unsold at the termination of
                           the offering.

         (b) The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial BONA FIDE offering thereof.

         (h) Insofar as indemnification for liabilities arising under the
Securities Act of 1933 (the "Act") may be permitted to directors, officers and
controlling persons of the Registrant pursuant to the foregoing provisions, or
otherwise, the Registrant has been advised that in the opinion of the Securities
and Exchange Commission such indemnification is against public policy as
expressed in the Act and is, therefore, unenforceable. In the event that a claim
for indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.

                                      II-4
<PAGE>

                                   SIGNATURES

                                 THE REGISTRANT

         Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the Town of Billerica, Commonwealth of Massachusetts, on December
31, 2000.

                                          AMERICAN SCIENCE AND ENGINEERING, INC.
                                          (Registrant)

                                          /s/ Ralph S. Sheridan
                                          --------------------------------------
                                          By: Ralph S. Sheridan, President

                                POWER OF ATTORNEY

         KNOW ALL MEN BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Ralph S. Sheridan and Lee C. Steele, and
each of them (with full power to each of them to act alone), his and true and
lawful attorneys-in-fact and agents, with full power of substitution and
re-substitution, for him and in his name, place and stead, in any and all
capacities, to sign any and all amendments (including post-effective amendments)
to this Registration Statement, and to file the same, with all exhibits thereto
and other documents in connection therewith, with the Securities and Exchange
Commission, granting unto said attorneys-in-fact and agents, and each of them,
full power and authority to do and perform each and every act and thing
requisite and necessary to be done in and about the premises as fully to all
intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorneys-in-fact and agents, or any of them, or their
substitutes, may lawfully do or cause to be done by virtue hereof.

         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.

<TABLE>
<CAPTION>
NAME                                     CAPACITY                                      DATE
<S>                                      <C>                                           <C>
/s/ Ralph S. Sheridan                    President, Chief Executive                    December 31, 2000
----------------------------------       Officer and Director
Ralph S. Sheridan                        (Principal Executive
                                         Officer)

                                         Director                                      December __, 2000
----------------------------------
Herman Feshbach

/s/ Roger P. Heinisch                    Director                                      December 31, 2000
----------------------------------
Roger P. Heinisch

/s/ Hamilton W. Helmer                   Director                                      December 31, 2000
--------------------------------
Hamilton W. Helmer

/s/ Donald J. McCarren                   Director                                      December 31, 2000
---------------------------------
Donald J. McCarren

/s/ William E. Odom                      Director, Chairman of the                     December 31, 2000
---------------------------------        Board of Directors
William E. Odom

/s/ Carl W. Vogt                         Director                                      December 31, 2000
----------------------------------
Carl W. Vogt
</TABLE>

<PAGE>

                                  EXHIBIT INDEX
<TABLE>
<CAPTION>
NUMBER EXHIBIT    DESCRIPTION OF EXHIBIT                                                                      PAGE
<S>               <C>                                                                                         <C>

4.1               Restated Articles of Organization of the Registrant, as
                  amended by: (a) Articles of Amendment dated October 29, 1976;
                  (b) Articles of Amendment dated May 17, 1976; (c) Articles of
                  Amendment dated March 28, 1973; (d) Articles of Amendment
                  dated November 5, 1996 (each of the foregoing is filed as
                  Exhibit 4.1 to the Registrant's Registration Statement on Form
                  S-8 filed on May 28, 1997 (Reg. No. 333-27929) with respect to
                  the Registrant's Executive Equity Incentive Plan); and (e)
                  Certificate of Vote of Directors Establishing a Class or
                  Series of Stock dated April 14, 1998 (filed as Exhibit 4.1 to
                  the Registrant's Registration Statement on Form S-8 filed on
                  December 24, 1998 (Reg. No. 333-69717) with respect to the
                  Registrant's 1998 Non-Qualified Stock Option Plan).                                            *

4.2               By-Laws of the Registrant, as amended (filed as Exhibit
                  2(a)(iii) to Registrant's Registration Statement on Form S-7,
                  Registration No. 2-56452 (the "Form S-7")).                                                    *

4.3               Specimen Certificate of Common Stock (filed as Exhibit 2(a)(i)
                  to the Form S-7).                                                                              *

4.4               Shareholder Rights Agreement (the "Rights Agreement") dated as
                  of April 17, 1998 between Registrant and American Stock
                  Transfer & Trust Co., Inc., as Rights Agent (filed as Exhibit
                  4 to the Current Report on Form 8-K filed on April 15, 1998).                                  *

5.1               Legal Opinion of Brown, Rudnick, Freed & Gesmer.                                              11

23.1              Consent of Brown, Rudnick, Freed & Gesmer.                                                    **

23.2              Consent of Arthur Andersen LLP.                                                               15

24                Power of Attorney.                                                                           ***

99                American Science and Engineering, Inc. 2000 Combination Stock
                  Option Plan. (filed as Exhibit A to the Definitive Proxy
                  Statement on Schedule 14A filed on August 18, 2000).                                           *
</TABLE>

---------------------------------------------------
*        Not filed herewith. In accordance with Rule 411(c) promulgated pursuant
         to the Securities Act of 1933, as amended, reference is made to the
         documents previously filed with the Securities and Exchange Commission
         which documents are hereby incorporated by reference.
**       Contained in Exhibit 5.
***      Included on Signature Page of this Registration Statement.
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{"company-data": {"conformed-name": "AMERICAN SCIENCE & ENGINEERING INC", "cik": "0000005768", "assigned-sic": "3844", "irs-number": "042240991", "state-of-incorporation": "MA", "fiscal-year-end": "0331"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-53842", "film-number": "1510433"}, "business-address": {"street1": "829 MIDDLESEX TURNPIKE", "street2": "40 ERIE STREET", "city": "BILLERICA", "state": "MA", "zip": "01821", "phone": "9782629700"}, "mail-address": {"street1": "40 ERIE STREET", "street2": "829 MIDDLESEX TURNPIKE", "city": "BILLERICA", "state": "MA", "zip": "01821"}}
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JANUARY 17, 2001.
                                                           REGISTRATION NO. 333-
================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                     ---------------------------------------

                     AMERICAN SCIENCE AND ENGINEERING, INC.
             ------------------------------------------------------
             (Exact Name of Registrant as Specified in Its Charter)

          MASSACHUSETTS                                         04-2440991
---------------------------------                          ---------------------
(State or Other Jurisdiction of                              (I.R.S. Employer
 Incorporation or Organization                              Identification No.)

                   829 MIDDLESEX TURNPIKE, BILLERICA, MA        01821
            ------------------------------------------------------------
               (Address of Principal Executive Offices)       (Zip Code)

                                 ---------------

                     AMERICAN SCIENCE AND ENGINEERING, INC.
                       2000 COMBINATION STOCK OPTION PLAN
                       ----------------------------------
                            (Full Title of the Plan)

                            STEVEN R. LONDON, ESQUIRE
                         BROWN, RUDNICK, FREED & GESMER
                              ONE FINANCIAL CENTER
                          BOSTON, MASSACHUSETTS 02111
                     ---------------------------------------
                     (Name and Address of Agent for Service)

                                 (617) 856-8200
                      -------------------------------------
          (Telephone Number, Including Area Code, of Agent for Service)

                         CALCULATION OF REGISTRATION FEE
=================================================================================================================
                                                        Proposed            Proposed
                                      Amount             Maximum       Maximum Aggregate
    Title of Each Class of            to be          Offering Price    Offering Price (1)        Amount of
 Securities to be Registered        Registered        Per Share (1)                          Registration Fee
-----------------------------------------------------------------------------------------------------------------
Common Stock,                      440,000 (2)        $4.53125 (3)       $1,993,750 (3)             $498.44
$.66 2/3 par value

Rights to Purchase                 440,000                 0   (5)                0 (5)                   0(5)
Common Stock (4)
=================================================================================================================
(1) Estimated solely for the purpose of determining the registration fee
pursuant to Rule 457(h) under the Securities Act of 1933, as amended.

     (2) Such presently indeterminable number of additional shares of Common
Stock are also registered hereunder as may be issued in the event of a merger,
consolidation, reorganization, recapitalization, stock dividend, stock split,
stock combination or other similar change in Common Stock.
(3) Based upon the average high and low prices for the Registrant's Common
Stock, $.66 2/3 par value (the "Common Stock"), on January 11, 2001 as reported
by the American Stock Exchange.

     (4) Pursuant to a Rights Agreement entered into in 1998, one right (each a
"Right") is deemed to be delivered with each outstanding share of Common Stock.
The 440,000 Rights registered hereby consist of 440,000 Rights which may be
issued with shares of Common Stock issuable upon exercise of options granted or
to be granted under the Registrant's 2000 Combination Stock Option Plan.

     (5) The Rights are not separately transferable apart from the Common Stock,
nor are they exercisable until the occurrence of certain events. Accordingly, no
independent value has been attributed to the Rights.
PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         The following documents are hereby incorporated by reference into this
Registration Statement:

         (a)      The Registrant's latest Annual Report on Form 10-K for the
                  fiscal year ended March 31, 2000 filed pursuant to Section
                  13(a) or 15(d) of the Securities Exchange Act of 1934, as
                  amended (the "Exchange Act");

         (b)      All other reports filed by the Registrant pursuant to Section
                  13(a) or 15(d) of the Exchange Act since the end of the fiscal
                  year covered by the Registrant's annual report referred to in
                  (a) above; and

         (c)      The description of the Registrant's Common Stock contained in
                  the Registrant's Registration Statement on Form 8-A (File No.
                  001-06549) pursuant to the Exchange Act with the Securities
                  and Exchange Commission (the "Commission"), and the
                  description of the Rights contained in the Registrant's
                  Registration Statement on Form 8-A, filed on April 15, 1998,
                  with the Commission, and all amendments thereto and reports
                  filed for the purpose of updating such descriptions.

         All documents filed by the Registrant pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Exchange Act, subsequent to the date hereof and
prior to the filing of a post-effective amendment which indicates that all
securities offered have been sold or which deregisters all securities then
remaining unsold, shall be deemed hereby incorporated by reference in this
Registration Statement and to be a part hereof from the date of filing of
such documents. Any statement contained in a document incorporated or deemed
to be incorporated by reference herein shall be deemed to be modified or
superseded for purposes of this registration statement to the extent that a
statement contained herein or in any subsequently filed document which also
is or is deemed to be incorporated by reference herein modifies or supersedes
such statement.

Item 4.  DESCRIPTION OF SECURITIES.

         Not Applicable.

Item 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

         The validity of the shares of Common Stock to be issued in accordance
with the American Science and Engineering, Inc. 2000 Combination Stock Option
Plan has been passed upon for the Registrant by Brown, Rudnick, Freed & Gesmer,
One Financial Center, Boston, Massachusetts 02111.

Item 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

        Section 67 of Chapter 156B of the Massachusetts General Laws permits the
indemnification of directors and officers to the extent authorized by the
Articles of Organization or By-Laws of a corporation or by a vote of the
stockholders. Except as otherwise provided by the Articles of Organization or
By-Laws, indemnification of persons who are not directors of a corporation may
be provided to the extent authorized by the directors. No indemnification may be
provided for any person with respect to any matter as to which he shall have
been adjudicated in any proceeding not to have acted in good faith in the
reasonable belief that his action was in the best interest of the corporation.

        Article VI of the Registrant's By-Laws provides, in substance, that the
Registrant shall indemnify any person who was or is a party or is threatened to
be made a party to any threatened, pending or completed action or suit, by

                                      II-1
reason of the fact that he is or was serving as a director or officer of the
Registrant or is or was serving at the request of the Registrant as a director,
trustee or officer of another corporation or entity. The indemnification
provisions apply to expenses actually incurred by such person in connection with
any civil action, suit or proceeding to which such person may be made a party,
or by which such person shall be threatened, by reason of any alleged act or
failure to act in his present or former capacity as a director or officer of the
Registrant or as a director, trustee or officer of such affiliated corporation
or entity. No person, however, has the right to indemnification in relation to
any matter as to which such person shall have been finally adjudged in any legal
proceeding not to have acted in good faith and the reasonable belief that the
person's action was in the best interest of the Registrant. In the event of any
settlement of any action, suit or proceeding, the right to indemnification is
limited to matters as to which the Registrant is advised by counsel that such
settlement is reasonable and that such person has acted in good faith and the
reasonable belief that his action was in the best interest of the Registrant.
The right of indemnification contained in the Registrant's By-Laws is
non-exclusive and is in addition to any other rights such person may have.

         The Registrant has also entered into indemnification agreements with
all of its directors and executive officers (the "Indemnitees"). In general,
these agreements provide that the Registrant will indemnify and advance expenses
to the Indemnitees to the fullest extent permitted by law. More specifically,
the Registrant must indemnify the Indemnitees if, by reason of the Indemnitee's
corporate status, the Indemnitee is, or is threatened to be made, a party to or
is otherwise involved in any legal proceeding brought by: (1) persons other than
the Registrant; or (2) or in the right of the Registrant. The Indemnitee will
only be indemnified, however, if the Indemnitee acted in good faith and is
adjudged not to have received an improper personal benefit. In a claim brought
by or on behalf of the Registrant, no indemnification will be made if the
Indemnitee is adjudged to be liable to the Registrant unless a court deciding
the matter decides otherwise. Finally, notwithstanding the foregoing discussion,
if an Indemnitee is successful on the merits of a proceeding, the Indemnitee
will be indemnified to the maximum extent permitted by law from all expenses,
judgments, penalties, fines and amounts paid in settlement, actually and
reasonably incurred.

Item 7.  EXEMPTION FROM REGISTRATION CLAIMED.

         Not Applicable.

                                      II-2
Item 8.  EXHIBITS.
NUMBER EXHIBIT    DESCRIPTION OF EXHIBIT                                                   PAGE
4.1               Restated Articles of Organization of the Registrant, as
                  amended by: (a) Articles of Amendment dated October 29, 1976;
                  (b) Articles of Amendment dated May 17, 1976; (c) Articles of
                  Amendment dated March 28, 1973; (d) Articles of Amendment
                  dated November 5, 1996 (each of the foregoing is filed as
                  Exhibit 4.1 to the Registrant's Registration Statement on Form
                  S-8 filed on May 28, 1997 (Reg. No. 333-27929) with respect to
                  the Registrant's Executive Equity Incentive Plan); and (e)
                  Certificate of Vote of Directors Establishing a Class or
                  Series of Stock dated April 14, 1998 (filed as Exhibit 4.1 to
                  the Registrant's Registration Statement on Form S-8 filed on
                  December 24, 1998 (Reg. No. 333-69717) with respect to the
                  Registrant's 1998 Non-Qualified Stock Option Plan).                         *

4.2               By-Laws of the Registrant, as amended (filed as Exhibit
                  2(a)(iii) to Registrant's Registration Statement on Form S-7,
                  Registration No. 2-56452 (the "Form S-7")).                                 *

4.3               Specimen Certificate of Common Stock (filed as Exhibit 2(a)(i)
                  to the Form S-7).                                                           *

4.4               Shareholder Rights Agreement (the "Rights Agreement") dated as
                  of April 17, 1998 between Registrant and American Stock
                  Transfer & Trust Co., Inc., as Rights Agent (filed as Exhibit
                  4 to the Current Report on Form 8-K filed on April 15, 1998).               *

5.1               Legal Opinion of Brown, Rudnick, Freed & Gesmer.                           11

23.1              Consent of Brown, Rudnick, Freed & Gesmer.                                 **

23.2              Consent of Arthur Andersen LLP.                                            15

24                Power of Attorney.                                                        ***

99                American Science and Engineering, Inc. 2000 Combination Stock
                  Option Plan. (filed as Exhibit A to the Definitive Proxy
                  Statement on Schedule 14A filed on August 18, 2000).                        *
---------------------------------------------------
*        Not filed herewith. In accordance with Rule 411(c) promulgated pursuant
         to the Securities Act of 1933, as amended, reference is made to the
         documents previously filed with the Securities and Exchange Commission
         which documents are hereby incorporated by reference.
**       Contained in Exhibit 5.
***      Included on Signature Page of this Registration Statement.

                                      II-3
Item 9.  UNDERTAKINGS.

         (a)      The undersigned Registrant hereby undertakes:

                  (1)      To file, during any period in which offers or sales
                           are being made, a post-effective amendment to this
                           Registration Statement to include any material
                           information with respect to the plan of distribution
                           not previously disclosed in the Registration
                           Statement or any material change to such information
                           in the Registration Statement.

                  (2)      That, for the purpose of determining any liability
                           under the Securities Act of 1933, each such
                           post-effective amendment shall be deemed to be a new
                           registration statement relating to the securities
                           offered therein, and the offering of such securities
                           at that time shall be deemed to be the initial BONA
                           FIDE offering thereof.

                  (3)      To remove from registration by means of a
                           post-effective amendment any of the securities being
                           registered which remain unsold at the termination of
                           the offering.

         (b) The undersigned Registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial BONA FIDE offering thereof.

         (h) Insofar as indemnification for liabilities arising under the
Securities Act of 1933 (the "Act") may be permitted to directors, officers and
controlling persons of the Registrant pursuant to the foregoing provisions, or
otherwise, the Registrant has been advised that in the opinion of the Securities
and Exchange Commission such indemnification is against public policy as
expressed in the Act and is, therefore, unenforceable. In the event that a claim
for indemnification against such liabilities (other than the payment by the
Registrant of expenses incurred or paid by a director, officer or controlling
person of the Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the Registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.

                                      II-4
SIGNATURES

                                 THE REGISTRANT

         Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the Town of Billerica, Commonwealth of Massachusetts, on December
31, 2000.

                                          AMERICAN SCIENCE AND ENGINEERING, INC.
                                          (Registrant)

                                          /s/ Ralph S. Sheridan
                                          --------------------------------------
                                          By: Ralph S. Sheridan, President

                                POWER OF ATTORNEY

         KNOW ALL MEN BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Ralph S. Sheridan and Lee C. Steele, and
each of them (with full power to each of them to act alone), his and true and
lawful attorneys-in-fact and agents, with full power of substitution and
re-substitution, for him and in his name, place and stead, in any and all
capacities, to sign any and all amendments (including post-effective amendments)
to this Registration Statement, and to file the same, with all exhibits thereto
and other documents in connection therewith, with the Securities and Exchange
Commission, granting unto said attorneys-in-fact and agents, and each of them,
full power and authority to do and perform each and every act and thing
requisite and necessary to be done in and about the premises as fully to all
intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorneys-in-fact and agents, or any of them, or their
substitutes, may lawfully do or cause to be done by virtue hereof.

         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.
NAME                                     CAPACITY                                      DATE
/s/ Ralph S. Sheridan                    President, Chief Executive                    December 31, 2000
----------------------------------       Officer and Director
Ralph S. Sheridan                        (Principal Executive
                                         Officer)

                                         Director                                      December __, 2000
----------------------------------
Herman Feshbach

/s/ Roger P. Heinisch                    Director                                      December 31, 2000
----------------------------------
Roger P. Heinisch

/s/ Hamilton W. Helmer                   Director                                      December 31, 2000
--------------------------------
Hamilton W. Helmer

/s/ Donald J. McCarren                   Director                                      December 31, 2000
---------------------------------
Donald J. McCarren

/s/ William E. Odom                      Director, Chairman of the                     December 31, 2000
---------------------------------        Board of Directors
William E. Odom

/s/ Carl W. Vogt                         Director                                      December 31, 2000
----------------------------------
Carl W. Vogt
EXHIBIT INDEX
NUMBER EXHIBIT    DESCRIPTION OF EXHIBIT                                                                      PAGE
4.1               Restated Articles of Organization of the Registrant, as
                  amended by: (a) Articles of Amendment dated October 29, 1976;
                  (b) Articles of Amendment dated May 17, 1976; (c) Articles of
                  Amendment dated March 28, 1973; (d) Articles of Amendment
                  dated November 5, 1996 (each of the foregoing is filed as
                  Exhibit 4.1 to the Registrant's Registration Statement on Form
                  S-8 filed on May 28, 1997 (Reg. No. 333-27929) with respect to
                  the Registrant's Executive Equity Incentive Plan); and (e)
                  Certificate of Vote of Directors Establishing a Class or
                  Series of Stock dated April 14, 1998 (filed as Exhibit 4.1 to
                  the Registrant's Registration Statement on Form S-8 filed on
                  December 24, 1998 (Reg. No. 333-69717) with respect to the
                  Registrant's 1998 Non-Qualified Stock Option Plan).                                            *

4.2               By-Laws of the Registrant, as amended (filed as Exhibit
                  2(a)(iii) to Registrant's Registration Statement on Form S-7,
                  Registration No. 2-56452 (the "Form S-7")).                                                    *

4.3               Specimen Certificate of Common Stock (filed as Exhibit 2(a)(i)
                  to the Form S-7).                                                                              *

4.4               Shareholder Rights Agreement (the "Rights Agreement") dated as
                  of April 17, 1998 between Registrant and American Stock
                  Transfer & Trust Co., Inc., as Rights Agent (filed as Exhibit
                  4 to the Current Report on Form 8-K filed on April 15, 1998).                                  *

5.1               Legal Opinion of Brown, Rudnick, Freed & Gesmer.                                              11

23.1              Consent of Brown, Rudnick, Freed & Gesmer.                                                    **

23.2              Consent of Arthur Andersen LLP.                                                               15

24                Power of Attorney.                                                                           ***

99                American Science and Engineering, Inc. 2000 Combination Stock
                  Option Plan. (filed as Exhibit A to the Definitive Proxy
                  Statement on Schedule 14A filed on August 18, 2000).                                           *
---------------------------------------------------
*        Not filed herewith. In accordance with Rule 411(c) promulgated pursuant
         to the Securities Act of 1933, as amended, reference is made to the
         documents previously filed with the Securities and Exchange Commission
         which documents are hereby incorporated by reference.
**       Contained in Exhibit 5.
***      Included on Signature Page of this Registration Statement.