<PAGE>


                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  AMENDMENT #1
                                   FORM 10-K/A

/x/  ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
     ACT OF 1934 [FEE REQUIRED]

     For the fiscal year ended March 31, 1998 
                                       OR

/ /  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
     EXCHANGE ACT OF 1934 

                         Commission file number 1-6549

                     AMERICAN SCIENCE AND ENGINEERING, INC.
             (Exact name of registrant as specified in its charter)

Massachusetts                               04-2240991
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
incorporation or organization)

829 Middlesex Turnpike, Billerica, Massachusetts            01821
(Address of principal executive offices)                    (Zip Code)

Registrant's telephone number, including area code          (978) 262-8700

Securities registered pursuant to Section 12(b) of the Act:
<TABLE>
<CAPTION>

Title of each class                         Name of each exchange on which registered
-------------------                         -----------------------------------------
<S>                                         <C>
Common Stock ($.66 2/3 par value)           American Stock Exchange
</TABLE>

Securities registered pursuant to Section 12(g) of the Act:  None

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days. YES  x  NO
                                       ---    ---

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405
of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K.  X
           ---

The aggregate market value of voting stock held by non-affiliates of the
registrant on June 30, 1998 was $67,776,063

4,780,202 shares of Registrant's Common Stock were outstanding on June 30, 1998.

                     The Exhibit Index is located on page 49
                               PAGE 1 OF 76 PAGES


<PAGE>


         The undersigned registrant hereby amends the following portion of its
Annual Report on Form 10-K dated July, 1998 ("Form 10K") as set forth below:


ITEM 11.   EXECUTIVE COMPENSATION

/ / The following chart provides information concerning compensation paid by the
    Company during the year ended March 31, 1998 to the Chief Executive Officer
    and each of the four most highly compensated executive officers of the
    Company whose aggregate compensation exceeded $100,000.

                              SUMMARY COMPENSATION
<TABLE>
<CAPTION>


                                                                             Long-Term
                                                       Annual                 Compen-
                                                    Compensation               sation
                                            -----------------------------
                                                                                                    All
Name and Principal            Fiscal                                           Option          Other Compen-
Position                      Year          Salary ($)         Bonus ($)     Awards (#)        sation ($) (1)
------------------------      ------        ---------          ---------     ----------        --------------

<S>                            <C>           <C>              <C>            <C>               <C>  
Ralph S. Sheridan              1998          240,000             230,000             0             7,729
President and CEO              1997          222,213             270,385(3)    225,000             4,479
                               1996          200,000             202,168(3)          0             2,486
                                                          
Jeffrey A. Bernfeld            1998          130,000              30,000        20,000               408
Vice President, General        1997          120,408              19,000        16,000               408
Counsel                        1996(2)         7,846                N.A.        24,000               408
                                                          
Peter W. Harris                1998          120,192              45,000             0               403
Vice President,                1997          111,941              45,000        30,000               403
Sales / Marketing              1996          110,000              40,000             0               403
                                                          
Alan H. Rutan                  1998          115,112              12,000        16,000             1,748
Vice President,                1997(2)        87,132                  --        24,000             1,748
Engineering                                               
                                                          
                                                          
Lee C. Steele                  1998          125,077              29,750        30,000               752
Vice President and CFO         1997          120,560              27,000             0               752
                               1996          110,752              27,000             0             1,344
                                                          
</TABLE>
                                                        
(1)  All Other Compensation includes imputed income from taxable life insurance
     premiums paid by the Company, and, for Mr. Sheridan, a leased automobile.

(2)  The indicated years were years of partial employment with the Company for
     the named executive.

(3)  Mr. Sheridan's bonus is paid in respect of "contract years" ending
     September 30th in each year and is paid in cash, except in fiscal years
     1996 and 1997 when the bonus also included Company stock and payments made
     to him to alleviate the tax impact of the stock bonus.

                                       2
<PAGE>


Mr. Sheridan has an employment contract with the Company that provides for his
employment as President and Chief Executive Officer, and as a Director, through
September 1999, at an annual salary of $240,000, subject to annual review, plus
performance bonuses tied to specific accomplishments. This contract replaces Mr.
Sheridan's original contract with the Company, which expired in September 1996.

Under the contract, Mr. Sheridan is eligible to receive an annual bonus of up to
$230,000 in each contract year, based on his accomplishment of goals established
by the Compensation Committee. Under the previous contract, but not under the
current contract, Mr. Sheridan also received a bonus of up to 10,000 shares of
common stock and an amount calculated to compensate him for the taxes due on the
stock portion of this bonus. In addition, in October 1996 the Company granted
Mr. Sheridan options to purchase 225,000 shares of the Company's Common Stock at
an exercise price of $14.00 per share, the fair market value of the Company's
Common Stock on the date of grant. The options become exercisable at the rate of
75,000 options per year on the first three anniversaries of the grant.

Mr. Sheridan recognized no income upon the issuance of the options. When the
options are exercised, Mr. Sheridan will recognize ordinary income in an amount
equal to the difference between the fair market value of the Common Stock
received upon the exercise of the option and the amount paid for the Common
Stock. At that time, the Company will be allowed a deduction equal to the amount
recognized as ordinary income by Mr. Sheridan. The options provide that to the
extent that exercise of an option would give rise to compensation expense that
the Company reasonably expects will not be deductible for tax purposes in any
given taxable year pursuant to Section 162(m) of the Internal Revenue Code of
1986, as amended, the number of shares as to which the options may be exercised
during that taxable year shall be limited.

Under his initial employment contract, Mr. Sheridan purchased 160,000 treasury
shares of the Company's Common Stock payable by promissory note. The note is due
on the earlier of September 15, 2003 or the termination of Mr. Sheridan's
employment. The Company has agreed to reimburse Mr. Sheridan for the interest
payable under the note in most circumstances.

Mr. Sheridan is entitled to receive the same benefits as other senior executives
of the company, as well as to the use of a car.

In the event that Mr. Sheridan's employment with the Company is terminated
without Cause, or by him for Good Reason (as defined in the employment
contract), he will receive twelve months' pay and any previously earned bonuses.
In the event that Mr. Sheridan's employment with the Company is terminated for
Cause, or by him other than for Good Reason (as defined in the employment
contract), or by his death or disability, he will not be entitled to receive any
salary beyond the date of termination, and he will only be entitled to receive
previously earned bonuses if the termination is caused by death or disability.

Mr. Bernfeld has an agreement with the Company which provides for a minimum base
salary of $120,000, adjustable at the discretion of the President, and a bonus
of up to $20,000 subject to the achievement of individual and corporate goals;
and 24,000 stock options granted at market price, which vest according to a
schedule. The agreement is for a three year term ending in February, 1999, and
grants Mr. Bernfeld severance payments equal to one year's salary if he is
terminated in connection with a change of the control of the Company as defined
in the agreement. The agreement also provides that if Mr. Bernfeld is terminated
for any reason other than "Cause" as defined in the agreement, he will be
entitled to receive an amount equal to at least six months salary.

                                       3

<PAGE>


Dr. Callerame and Messrs. Rutan and Steele have agreements with the Company
granting each of them severance payments equal to one year's salary if he is
terminated in connection with a change of control of the Company as defined in
the agreement. The agreement also provides that if each of them is terminated
for any reason other than "Cause" as defined in the agreement, he will be
entitled to receive an amount equal to at least six months salary.


/ /  The following tables provide information concerning the grant of options
     in Fiscal Year 1998 to Executive Officers named in the Summary Compensation
     Table and options exercised by those officers.


                      OPTION GRANTS IN THE LAST FISCAL YEAR
<TABLE>
<CAPTION>


                                       Individual Grants                          Potential Realizable Value at
                          ---------------------------------------------------     Assumed Annual Rates of Stock
                                                                                  Price Appreciation for Option
                                                                                  Term ($)
                                                                                  ------------------------------

                                        % of Total
                                           Options
                          Options   Granted to All      Exercise     Expiration
                          Granted        Employees      Price ($)       Date             5%/year      10%/year
                          --------------------------------------------------------------------------------------

<S>                        <C>       <C>              <C>          <C>                <C>            <C>

Ralph S. Sheridan                0             N/A          N/A           N/A             N/A            N/A
Jeffrey A. Bernfeld         20,000            6.98       11.125      11/20/07         221,374        484,295
Peter W. Harris                  0             N/A          N/A           N/A             N/A            N/A
Alan H. Rutan               16,000            5.58       11.125      11/20/07         177,099        387,436
Lee C. Steele               30,000           10.47       11.125      11/20/07         332,061        726,442

</TABLE>



                 AGGREGATED OPTION EXERCISES IN LAST FISCAL YEAR
                        AND FISCAL YEAR END OPTION VALUES

<TABLE>
<CAPTION>

                                                                Number of           Value of Unexercised In-
                                                          Unexercised Options       The-Money Options at 
                                 Shares                   at Fiscal Year End -      Fiscal Year End -
                               Acquired                   March 31, 1998 (#)        March 31, 1998 ($)
                                   on         Value       --------------------      ------------------
                                Exercise     Realized     Exer-       Unexer-        Exer-         Unexer-
                                  (#)          ($)       cisable      cisable       cisable        cisable
                              ----------------------------------------------------------------------------
                      
<S>                            <C>            <C>        <C>           <C>          <C>               <C>
Ralph S. Sheridan                0              0        195,000        150,000      2,176,875              0
Jeffrey A. Bernfeld              0              0         30,000         30,000        107,250         85,750
Peter W. Harris                  0              0         40,000         20,000        318,250         75,000
Alan H. Rutan                    0              0         12,000         28,000         43,500         83,500
Lee C. Steele                    0              0         50,000         30,000        409,375         75,000

</TABLE>


                                       4

<PAGE>

/ /  Compensation of Directors

Directors who are also employees of the Company do not receive additional
compensation as Directors. Non-Employee Directors (other than the Chairman)
receive annual compensation of 2,000 shares of Company Common Stock issuable on
January 10th in each year, and options to purchase 7,000 shares of Common Stock
at the closing price on the date of the Annual Meeting in each year. The
Chairman receives 2,500 shares of Common Stock on January 10th in each year as
well as cash payments totaling $14,331 in fiscal 1998 and continues to receive
deferred compensation under a now discontinued plan described below. No meeting
fees or other fees are payable to any Director. See Item 13 - Certain
Relationships and Related Transactions for additional information concerning
certain Directors.

Dr. Feshbach, the Company's Chairman, is covered by a nonfunded deferred
compensation plan (adopted in 1976 and amended in 1977, 1980, 1986, 1990 and
1992) that provides for periodic payments beginning at age 65, based on length
of service. During the year, Dr. Feshbach received $4,752 under the Plan. The
Company accrues the current cost of the plan, which amounted to $10,000 in
fiscal 1998.

/ /  Compensation Committee Interlocks, Insider Participation and Section 16
     Reporting

During the fiscal year ended March 31, 1998, the Company's Compensation
Committee consisted of Dr. Herman Feshbach, Dr. Hamilton W. Helmer and Dr.
Donald J. McCarren. No reportable relationship existed with respect to any
member of the Compensation Committee.

Section 16(a) of the Securities Exchange Act of 1934 requires certain persons,
including the Company's Directors and Executive Officers, to file initial
reports of beneficial ownership of the Company's securities and reports of
changes in beneficial ownership with the Securities and Exchange Commission. For
fiscal year 1998, the Company believes that all required reports were filed on
time.

/ /  Board Compensation Committee Report on Executive Compensation

The Compensation Committee of the Board of Directors (consisting of the three
outside Directors whose names appear below this Report) has sole responsibility
for compensation issues relating to the Chief Executive Officer. Compensation
practices and policies for the other executive officers are set by the Chief
Executive Officer with the advice of the Compensation Committee.

The Compensation Committee has formulated an approach to all executive
compensation that emphasizes the establishment of goals and objectives for each
executive and for the Company as a whole and ties a substantial portion of
executive compensation to the performance of the executive and the Company with
respect to these goals and objectives. Base compensation for executive officers
(and many other Company employees) is established on the basis of an analysis of
salaries received by comparable employees of high-tech and manufacturing
companies in the Greater Boston area, company financial results and prospects,
and individual contributions relative to the job description and past
performance of each officer.

In line with this approach, the Company entered into a new employment agreement
with its President and Chief Executive Officer, Mr. Ralph S. Sheridan, in 1996
(effective as of September 1996). This Agreement was based, in part, on an
independent consultant's analysis of compensation arrangements for chief
executives of comparable companies, and was also based on a careful review of
the most important goals and objectives for the Company. The Agreement

                                       5

<PAGE>


provides for annual cash compensation of $240,000, plus annual incentive bonuses
of up to $230,000 tied to specific, agreed upon performance criteria. In
addition, in order to provide for long-term incentives, the Company has issued
to Mr. Sheridan nonstatutory stock options to purchase 225,000 shares of Common
Stock which vest ratably over three years.

For the contract year ended in September 1997, the Committee awarded Mr.
Sheridan a cash bonus of $230,000, representing 100% of the potential award
under his contract. This award represents the Committee's determination that Mr.
Sheridan had done an excellent job over the preceding twelve months and had met
all of the goals and objectives jointly established by the Committee and Mr.
Sheridan.

Also in keeping with its performance-based compensation philosophy, in the
spring of 1994, the Company implemented an incentive compensation program for
all executives who report directly to the Office of the President. Under this
new policy, these executives receive a specified portion of their total
compensation (ranging from 10% to 50%) based upon two factors: their completion
of agreed upon goals and objectives, and the performance of the entire Company.

Report Submitted By: Dr. Herman Feshbach, Dr. Hamilton W. Helmer and Dr. Donald
J. McCarren.


                                       6

<PAGE>





/ /  Stock Performance Chart

The following chart graphs the performance of the cumulative total return to
shareholders (stock price appreciation plus dividends) during the previous five
years in comparison to the returns of the Standard & Poor's 500 Composite Stock
Price Index and the Standard & Poor's 500 High-Tech Composite Stock Price Index.


                             [GRAPHIC OMITTED]

<TABLE>
<CAPTION>

                                            INDEXED RETURNS
                                            Years Ending
                                 Base
                                 Period
Company/Index                    Mar93      Mar94    Mar95   Mar96   Mar97   Mar98
----------------------------------------------------------------------------------
<S>                              <C>       <C>      <C>      <C>     <C>     <C>

AMERICAN SCIENCE ENGINEERING      100       46.97    75.76   119.70  146.97  165.15
S&P 500 INDEX                     100      101.48   117.25   154.77  185.40  274.39
TECHNOLOGY-500                    100      117.62   148.84   200.95  271.66  410.57

</TABLE>

Note: Assumes $100 invested at the close of trading on the last trading day
      preceding the first day of the fifth preceding fiscal year (and
      reinvestment of dividends) in the Company's Common Stock, Standard & 
      Poor's 500 Composite Stock Price Index and the Standard & Poor's 500 High-
      Tech Composite Stock Price Index.


                                       7

<PAGE>


                                    SIGNATURE


Pursuant to the requirements of Section 12b-15 of the Securities Exchange Act of
1934, the Company has duly caused this amendment to be signed on its behalf by
the undersigned, thereunto duly authorized.

                                      AMERICAN SCIENCE AND ENGINEERING, INC.

DATED: OCTOBER, 1998

                                      By: /s/ Jeffrey A. Bernfeld
                                          -----------------------
                                          Jeffrey A. Bernfeld, Vice President




                                       8