Registration
                                                                     Number 333-



                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
 
                                    FORM S-8
 
                             REGISTRATION STATEMENT
                                      under
                           THE SECURITIES ACT OF 1933
 
                         MERCURY COMPUTER SYSTEMS, INC.
               (Exact name of issuer as specified in its charter)

      Massachusetts                                     04-2741391
(State of Incorporation)                    (IRS Employer Identification Number)

                    199 Riverneck Road, Chelmsford, MA 01824
                    (Address of Principal Executive Offices)
 
                                 (978) 256-1300 
              (Registrant's telephone number, including area code)
 
                         MERCURY COMPUTER SYSTEMS, INC.
                             1982 Stock Option Plan
                             1991 Stock Option Plan
                1993 Stock Option Plan for Non-Employee Directors
                             1997 Stock Option Plan
                        1997 Employee Stock Purchase Plan
                            (Full title of the Plans)
 
                        Anthony J. Medaglia, Jr., Esquire
                           Hutchins, Wheeler & Dittmar
                           A Professional Corporation
                               l01 Federal Street
                           Boston, Massachusetts 02110
                                 (617) 951-6600 
            (Name, address and telephone number of agent for service)

<PAGE>
<TABLE>
<CAPTION>
                                         CALCULATION OF REGISTRATION FEE


Title of Securities to be            Amount to be         Proposed               Proposed               Amount of
Registered                           Registered           Maximum                Maximum                Registration Fee
                                     (1)                  Offering Price         Aggregate              (6)
                                                          Per Share              Offering Price

<S>                                  <C>                  <C>                     <C>                   <C>   
Common Stock (par value              2,052,958 (2)        $ 3.1157 (3)            $ 6,396,402           $1,887
$.01 per share)
                                     1,472,042 (4)        $ 16.5625 (5)           $24,380,696           $7,193

TOTAL AMOUNT                         3,525,000                                    $30,777,098           $9,080
                                     shares
 
</TABLE>
     -------------------  
(1)  Also registered  hereunder are such  additional  number of shares of Common
     Stock,  presently  indeterminable,  as  may be  necessary  to  satisfy  the
     antidilution provisions of the Plan to which this Registration Statement
     relates.

(2)  Represents  the sum of all shares  reserved for issuance  upon  exercise of
     options under the 1982 Stock Option Plan,  the 1991 Stock Option Plan,  the
     1993  Stock  Option  Plan for Non-  Employee  Directors  and the 1997 Stock
     Option  Plan  (collectively,   the  "Option  Plans")  which  are  currently
     outstanding,  plus all shares issued upon exercise of options granted under
     the Option Plans.

(3)  Represents the weighted  average  exercise price of options which have been
     granted  under the Option Plans which are either  outstanding  or have been
     exercised.

(4)  Represents  shares reserved for issuance upon exercise of options  reserved
     for grant under the Option Plans and shares reserved for issuance under the
     1997 Employee Stock Purchase Plan.

(5)  Represents  the  average of the high and low prices  reported on the NASDAQ
     National Market on May 18, 1998.

(6)  Determined in accordance  with Rule 457 of the  Securities  Act of 1933, as
     amended.
                                      - 2 -
<PAGE>
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


Item 3.  Incorporation of Documents by Reference

     The Company hereby  incorporates  by reference the documents  listed in (a)
through (c) below. In addition,  all documents subsequently filed by the Company
pursuant to Section 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of
1934 (prior to 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 to be  incorporated  by  reference  in this
Registration  Statement and to be a part thereof from the date of filing of such
documents.

     (a) The Company's latest Prospectus, dated January 29, 1998, filed pursuant
to Rule 424(b) under the Securities Act of 1933 which contains audited financial
statements for the Company's  latest fiscal year for which such  statements have
been filed.

     (b) All of the reports  filed by the Company  pursuant to Section  13(a) or
15(d) of the  Securities  Exchange  Act of 1934 since the end of the fiscal year
covered by the Prospectus referred to in (a) above.

     (c)  The  description  of  the  Company's  Common  Stock  contained  in the
Company's  Registration  Statement  on Form S-1,  File No.  333-41139,  filed on
November 26, 1997,  as amended on January 7, 1998,  January 23, 1998 and January
28, 1998.

Item 4.  Description of Securities

         Not applicable.

Item 5.  Interests of Named Experts and Counsel

     The validity of the  authorization and issuance of the Common Stock offered
hereby  will be passed upon for the Company by  Hutchins,  Wheeler & Dittmar,  A
Professional  Corporation,  Boston,  Massachusetts.  Anthony J. Medaglia, Jr., a
stockholder of Hutchins, Wheeler & Dittmar, A Professional Corporation,  and the
clerk of the Company  beneficially  owns 27,750 shares of the  Compan's  Common
Stock.  James Westra,  who is a stockholder  of Hutchins,  Wheeler & Dittmar,  A
Professional Corporation, beneficially owns 5,150 shares of the Company's Common
Stock.

                                      - 3 -
<PAGE>

Item 6.  Indemnification of Directors and Officers

     Section 67 of  Chapter  156B of the  General  Laws of the  Commonwealth  of
Massachusetts provides as follows:

     "Section 67.  Indemnification of directors,  officers,  employees and other
agents of a  corporation,  and persons  who serve at its  request as  directors,
officers, employees or other agents of another organization, or who serve at its
request in any  capacity  with  respect to any  employee  benefit  plan,  may be
provided by it to whatever extent shall be specified in or authorized by (i) the
articles of organization or (ii) a by-law adopted by the stockholders or (iii) a
vote  adopted by the  holders of a majority  of the shares of stock  entitled to
vote on the election of  directors.  Except as the articles of  organization  or
by-laws  otherwise  require,  indemnification  of any persons referred to in the
preceding  sentence who are not directors of the  corporation may be provided by
it to the extent authorized by the directors.  Such  indemnification may include
payment by the corporation of expenses incurred in defending a civil or criminal
action or  proceeding  in advance  of the final  disposition  of such  action or
proceeding,  upon receipt of an undertaking  by the person  indemnified to repay
such payment if he shall be  adjudicated  to be not entitled to  indemnification
under this section which  undertaking may be accepted  without  reference to the
financial ability of such person to make repayment. Any such indemnification may
be  provided  although  the person to be  indemnified  is no longer an  officer,
director,  employee or agent of the corporation or of such other organization or
no longer serves with respect to any such employee benefit plan.

     No  indemnification  shall 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 or to the extent that such matter relates to service
with  respect  to an  employee  benefit  plan,  in  the  best  interests  of the
participants or beneficiaries of such employee benefit plan.

     The absence of any express  provision for  indemnification  shall not limit
any right of indemnification existing independently of this section.

     A corporation shall have power to purchase and maintain insurance on behalf
of any person who is or was a director,  officer, employee or other agent of the
corporation,  or is or was  serving  at the  request  of  the  corporation  as a
director,  officer,  employee  or other  agent of another  organization  or with
respect to any employee benefit plan,  against any liability  incurred by him in
any such  capacity,  or arising  out of his  status as such,  whether or not the
corporation would have the power to indemnify him against such liability."

     Article 6 of the  Restated  Articles of  Organization,  as amended,  of the
Company reads as follows:


                                      - 4 -
<PAGE>

                                   Article 6.

     "Other lawful provisions for the conduct and regulation of the business and
affairs of the  Corporation,  for its  voluntary  dissolution  or for  limiting,
defining or  regulating  the powers of the  Corporation,  or of its directors or
stockholders, or of any class of stockholders are as follows: [...]

     No Director of the  Corporation  shall be liable to the  Corporation or its
stockholders  for monetary  damages for breach of  fiduciary  duty as a Director
notwithstanding  any statutory  provision or other law imposing such  liability,
except for liability of a director (i) for any breach of the Director's  duty of
loyalty to the Corporation or its  stockholders,  (ii) for acts or omissions not
in good faith or which involve intentional  misconduct or a knowing violation of
law,  (iii) under Section 61 or 62 of Chapter 156 of the  Massachusetts  General
Laws, or (iv) for any  transaction  from which the Director  derived an improper
personal benefit."
 

         Article 7 of the Amended By-Laws of the Company provides as follows:

                                   Article 7.

                   Indemnification of Directors and Officers 

Section 7.1        Definitions
 
     "For purposes of this Article 7:

(a)  'Director/officer'  means any  person  who is  serving  or has  served as a
Director,  officer or employee of the  Corporation  appointed  or elected by the
Board of Directors or the  stockholders  of the  Corporation,  or any  Director,
officer  or  employee  of the  Corporation  who is  serving or has served at the
request of the Corporation as a Director, officer, trustee, principal,  partner,
employee or other agent of any other organization.

(b)  'Proceeding'  means any  action,  suit or  proceeding,  civil or  criminal,
brought  or  threatened  in or before  any court,  tribunal,  administrative  or
legislative body or agency.

(c) 'Expense' means any fine or penalty,  and any liability fixed by a judgment,
order, decree or award in a Proceeding, any amount reasonably paid in settlement
of a Proceeding and any  professional  fees and other  disbursements  reasonably
incurred in connection with a Proceeding.

Section 7.2       Right to Indemnification

     Except as limited by law or as  provided  in  Sections  7.3 and 7.4 of this
Article 7, each  Director/officer  (and his heirs and personal  representatives)

                                     - 6 -
<PAGE>

shall be indemnified  by the  Corporation  against any Expense  incurred by such
Director/officer  in  connection  with  each  Proceeding  in  which he or she is
involved   as  a  result  of  his  or  her   serving  or  having   served  as  a
Director/officer.

Section 7.3       Indemnification Not Available

     No indemnification  shall be provided to a Director/officer with respect to
a Proceeding as to which it shall have been  adjudicated  that he or she did not
act in good  faith in the  reasonable  belief  that his or her action was in the
best interests of the Corporation.

Section 7.4       Compromise or Settlement

     In the event that a Proceeding  is  compromised  or settled so as to impose
any liability or obligation on a  Director/officer  or upon the Corporation,  no
indemnification  shall be provided as to said  Director/officer  with respect to
such Proceeding if such Director/officer shall have been adjudicated not to have
acted in good faith in the  reasonable  belief that his or her action was in the
best interests of the Corporation.

Section 7.5       Advances
 
     The Corporation shall pay sums on account of  indemnification in advance of
a final  disposition  of a  Proceeding  upon  receipt of an  undertaking  by the
Director/officer to repay such sums if it is subsequently established that he or
she is not entitled to indemnification  pursuant to Sections 7.3 and 7.4 hereof,
which  undertaking may be accepted without reference to the financial ability of
such person to make repayment.

Section 7.6       Not Exclusive
 
     Nothing in this Article 7 shall limit any lawful rights to  indemnification
existing independently of this Article 7.

Section 7.7       Insurance

     The  provisions of this Article 7 shall not limit the power of the Board of
Directors to authorize  the purchase and  maintenance  of insurance on behalf of
any  Director/officer  against any Expense whether or not the Corporation  would
have the power to indemnify  such  Director/officer  against such Expense  under
this Article 7."

Item 7.  Exemption from Registration Claimed

     Not Applicable.

                                      - 7 -
<PAGE>

Item 8.  Exhibits

<TABLE>
<CAPTION>
         Number              Description

<S>       <C>                <C>
          4.1                1982 Stock Option Plan (incorporated by reference to Exhibit 10.1 to the
                             Company's Registration Statement on Form S-1 (333-41139))

          4.2                1991 Stock Option Plan (incorporated by reference to Exhibit 10.2 to the
                             Company's Registration Statement on Form S-1 (333-41139))

          4.3                1993 Stock Option Plan for Non-Employee Directors (incorporated by
                             reference to Exhibit 10.3 to the Company's Registration Statement on
                             Form S-1 (333-41139))

          4.4                1997 Stock Option Plan (incorporated by reference to Exhibit 10.4 to the
                             Company's Registration Statement on Form S-1 (333-41139))

          4.5                The First Amendment to the 1997 Stock Option Plan filed herewith

          4.6                1997 Employee Stock Purchase Plan (incorporated by reference to
                             Exhibit 10.5 to the Company's Registration Statement on Form S-1
                             (333-41139))

          5.1                Opinion of Hutchins, Wheeler & Dittmar, A Professional Corporation

         23.1                Consent of Independent Public Accountants
 
         23.2                 Consent of Hutchins, Wheeler & Dittmar, A Professional Corporation
                              (included in Exhibit 5.1)
</TABLE>

Item 9.  Undertakings

        The undersigned Registrant hereby undertakes the following:

        (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:

               (i)  To include any  prospectus  required by Section  10(a)(3) of
                    the Securities Act of 1933;


                                      - 8 -
<PAGE>

               (ii) To reflect  in the  prospectus  any facts or events  arising
                    after the effective date of the  registration  statement (or
                    the most recent  post-effective  amendment  thereof)  which,
                    individually  or in the  aggregate,  represent a fundamental
                    change  in the  information  set  forth in the  registration
                    statement;

               (iii)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.

Provided,  however, that paragraphs (a)(l)(i) and (a)(l)(ii) do not apply if the
information  required  to be  included in a  post-effective  amendment  by those
paragraphs is contained in periodic reports filed by the Registrant  pursuant to
Section  13 or Section  15(d) of the  Securities  Exchange  Act of 1934 that are
incorporated by reference 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.

(c)  The   undersigned   Registrant   hereby   undertakes,   that,   insofar  as
indemnification  for liabilities arising under the Securities Act of 1933 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

                                      - 9 -
<PAGE>

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.



                                     - 10 -
<PAGE>
                                   SIGNATURES

     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 Chelmsford, Massachusetts on May 21, 1998.

                                        MERCURY COMPUTER SYSTEMS, INC.

                                        By /s/ James R. Bertelli 

                                          James R. Bertelli
                                          President

     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>
    Signature                                      Title                                      Date

<S>                                               <C>                                <C> 
/s/ James R. Bertelli                             President, Chief Executive         May 21, 1998
James R. Bertelli                                  Officer and Director



/s/ G. Mead Wyman                                  Vice President, Chief             May 21, 1998
G. Mead Wyman                                      Financial Officer and
                                                   Treasurer

 
/s/ Gordon B. Baty                                 Director                          May 21, 1998
Gordon B. Baty


/s/ R. Schorr Berman                               Director                          May 21, 1998
R. Schorr Berman


/s/ Albert P. Belle Isle                           Director                          May 21, 1998
Albert P. Belle Isle


/s/ Sherman N. Mullin                              Director                          May 21, 1998
Sherman N. Mullin

/s/ Melvin Sallen                                  Director                          May 21, 1998
Melvin Sallen

</TABLE>

                                     - 11 -
<PAGE>
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549







                                    EXHIBITS

                                       to

                                    FORM S-8






                             REGISTRATION STATEMENT

                                      under


                           THE SECURITIES ACT OF 1933









                         MERCURY COMPUTER SYSTEMS, INC.
             (Exact name of registrant as specified in its charter)

<PAGE>
Exhibit 4.5       First Amendment to the 1997 Stock Option Plan


                         MERCURY COMPUTER SYSTEMS, INC.

                             First Amendment to the
              Mercury Computer Systems, Inc. 1997 Stock Option Plan


     In accordance  with the  provisions  of Section 20 of the Mercury  Computer
Systems,  Inc.  1997  Stock  Option  Plan (the  "Plan"),  the Plan is amended as
follows:  

     1.  Section 2 of the Plan is hereby  amended  by  increasing  the number of
shares  subject to the Plan from Five Hundred  Seventy-Five  Thousand  (575,000)
shares to One Million Three Hundred Twenty-Five  Thousand  (1,325,000) shares of
the $.01 par value common stock of the Corporation.

     2. This  Amendment  shall take effect as of the date of its adoption by the
Mercury Computer  Systems,  Inc. Board of Directors and upon its approval by the
stockholders of Mercury Computer Systems, Inc. in accordance with the provisions
of Section 20 of the Plan.

     3.  Except  as  hereinabove  provided,  the  Plan is  hereby  ratified  and
confirmed in all respects.


                                        MERCURY COMPUTER SYSTEMS, INC.


                                        By:  /s/ Anthony J. Medaglia, Jr.
                                             Anthony J. Medaglia, Jr.
                                             Clerk

Adopted by the Board of Directors                    October 20, 1997

Adopted by the Stockholders                          December 18, 1997
<PAGE>
Exhibit 5.1  Opinion of Hutchins, Wheeler & Dittmar, A Professional Corporation

                                        May 21, 1998

Mercury Computer Systems, Inc.
199 Riverneck Road
Chelmsford, MA 01824

Ladies and Gentlemen:

     We are general counsel to Mercury Computer  Systems,  Inc., a Massachusetts
corporation  (the  "Company"),  and as such  counsel  we are  familiar  with the
corporate  proceedings  taken in  connection  with the adoption of the Company's
1982 Stock  Option  Plan,  1991 Stock  Option  Plan,  1993 Stock Option Plan for
Non-Employee Directors,  1997 Stock Option Plan and 1997 Employee Stock Purchase
Plan  (collectively  the "Plans").  We are also  familiar with the  registration
statement  on Form S-8 to which a copy of this  opinion  will be  attached as an
exhibit.

     As such counsel,  we have  examined the  corporate  records of the Company,
including the Restated Articles of Organization, By-laws, stock records, minutes
of meetings of its Board of Directors and  stockholders and such other documents
as we have deemed necessary as a basis for the opinions herein expressed.

     Based upon the foregoing,  and having regard for such legal  considerations
as we deem relevant, we are of the opinion that:

     1. The Company is duly organized and validly existing under the laws of the
Commonwealth of Massachusetts;

     2. The Company has authorized  the issuance of 25,000,000  shares of common
stock  having a par value of $.01 per share and  1,000,000  shares of  preferred
stock having a par value of $.01 per share.

     3. The shares of common stock issuable  pursuant to the Plans, when sold in
accordance  with the terms  thereof,  will be  legally  issued,  fully  paid and
non-assessable.
 
<PAGE>

Mercury Computer Systems, Inc.
May 21, 1998
Page 2

     We hereby  consent  to the  filing of this  opinion  as an  exhibit  to the
Registration  Statement on Form S-8 and to the reference to us under the caption
"Interests of Named Experts and Counsel" in the Registration Statement.


                                        Very truly yours,

                                        /s/Hutchins, Wheeler & Dittmar
                                        HUTCHINS, WHEELER & DITTMAR
                                        A Professional Corporation
<PAGE>
Exhibit 23.1               Consent of Independent Public Accountants


CONSENT OF INDEPENDENT ACCOUNTANTS

     We consent to the incorporation by reference in the Registration  Statement
of Mercury  Computer  Systems,  Inc.  (the  "Company") on Form S-8 of our report
dated August 28, 1997, except for the information in the final paragraph of Note
F, as to which the date is December 12, 1997, on our audits of the  consolidated
financial  statements  of the Company as of June 30, 1996 and 1997,  and for the
three years in the period ended June 30,  1997,  which report is included in the
Company's registration statement on Form S-1 (File No. 333-41139) filed with the
Securities and Exchange Commission pursuant to the Securities Act of 1933.


                                        Coopers & Lybrand L.L.P.


                                        /s/Coopers & Lybrand L.L.P.
Boston, Massachusetts
May 21, 1998
[{"type": "S-8", "sequence": "1", "description": "MERCURY FORM S-8", "secsgml_size_bytes": 27395}]
{"company-data": {"conformed-name": "MERCURY COMPUTER SYSTEMS INC", "cik": "0001049521", "assigned-sic": "3670", "irs-number": "042741391", "state-of-incorporation": "MA", "fiscal-year-end": "0630"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-53291", "film-number": "98629813"}, "business-address": {"street1": "199 RIVERNECK RD", "city": "CHELMSFORD", "state": "MA", "zip": "01824", "phone": "9782561300"}, "mail-address": {"street1": "199 RIVERNECK ROAD", "city": "CHELMSFORD", "state": "MA", "zip": "01824"}}
Registration
                                                                     Number 333-

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
 
                                    FORM S-8
 
                             REGISTRATION STATEMENT
                                      under
                           THE SECURITIES ACT OF 1933
 
                         MERCURY COMPUTER SYSTEMS, INC.
               (Exact name of issuer as specified in its charter)

      Massachusetts                                     04-2741391
(State of Incorporation)                    (IRS Employer Identification Number)

                    199 Riverneck Road, Chelmsford, MA 01824
                    (Address of Principal Executive Offices)
 
                                 (978) 256-1300 
              (Registrant's telephone number, including area code)
 
                         MERCURY COMPUTER SYSTEMS, INC.
                             1982 Stock Option Plan
                             1991 Stock Option Plan
                1993 Stock Option Plan for Non-Employee Directors
                             1997 Stock Option Plan
                        1997 Employee Stock Purchase Plan
                            (Full title of the Plans)
 
                        Anthony J. Medaglia, Jr., Esquire
                           Hutchins, Wheeler & Dittmar
                           A Professional Corporation
                               l01 Federal Street
                           Boston, Massachusetts 02110
                                 (617) 951-6600 
            (Name, address and telephone number of agent for service)
CALCULATION OF REGISTRATION FEE

Title of Securities to be            Amount to be         Proposed               Proposed               Amount of
Registered                           Registered           Maximum                Maximum                Registration Fee
                                     (1)                  Offering Price         Aggregate              (6)
                                                          Per Share              Offering Price
Common Stock (par value              2,052,958 (2)        $ 3.1157 (3)            $ 6,396,402           $1,887
$.01 per share)
                                     1,472,042 (4)        $ 16.5625 (5)           $24,380,696           $7,193

TOTAL AMOUNT                         3,525,000                                    $30,777,098           $9,080
                                     shares
-------------------  
(1)  Also registered  hereunder are such  additional  number of shares of Common
     Stock,  presently  indeterminable,  as  may be  necessary  to  satisfy  the
     antidilution provisions of the Plan to which this Registration Statement
     relates.

(2)  Represents  the sum of all shares  reserved for issuance  upon  exercise of
     options under the 1982 Stock Option Plan,  the 1991 Stock Option Plan,  the
     1993  Stock  Option  Plan for Non-  Employee  Directors  and the 1997 Stock
     Option  Plan  (collectively,   the  "Option  Plans")  which  are  currently
     outstanding,  plus all shares issued upon exercise of options granted under
     the Option Plans.

(3)  Represents the weighted  average  exercise price of options which have been
     granted  under the Option Plans which are either  outstanding  or have been
     exercised.

(4)  Represents  shares reserved for issuance upon exercise of options  reserved
     for grant under the Option Plans and shares reserved for issuance under the
     1997 Employee Stock Purchase Plan.

(5)  Represents  the  average of the high and low prices  reported on the NASDAQ
     National Market on May 18, 1998.

(6)  Determined in accordance  with Rule 457 of the  Securities  Act of 1933, as
     amended.
                                      - 2 -
PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3.  Incorporation of Documents by Reference

     The Company hereby  incorporates  by reference the documents  listed in (a)
through (c) below. In addition,  all documents subsequently filed by the Company
pursuant to Section 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of
1934 (prior to 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 to be  incorporated  by  reference  in this
Registration  Statement and to be a part thereof from the date of filing of such
documents.

     (a) The Company's latest Prospectus, dated January 29, 1998, filed pursuant
to Rule 424(b) under the Securities Act of 1933 which contains audited financial
statements for the Company's  latest fiscal year for which such  statements have
been filed.

     (b) All of the reports  filed by the Company  pursuant to Section  13(a) or
15(d) of the  Securities  Exchange  Act of 1934 since the end of the fiscal year
covered by the Prospectus referred to in (a) above.

     (c)  The  description  of  the  Company's  Common  Stock  contained  in the
Company's  Registration  Statement  on Form S-1,  File No.  333-41139,  filed on
November 26, 1997,  as amended on January 7, 1998,  January 23, 1998 and January
28, 1998.

Item 4.  Description of Securities

         Not applicable.

Item 5.  Interests of Named Experts and Counsel

     The validity of the  authorization and issuance of the Common Stock offered
hereby  will be passed upon for the Company by  Hutchins,  Wheeler & Dittmar,  A
Professional  Corporation,  Boston,  Massachusetts.  Anthony J. Medaglia, Jr., a
stockholder of Hutchins, Wheeler & Dittmar, A Professional Corporation,  and the
clerk of the Company  beneficially  owns 27,750 shares of the  Compan's  Common
Stock.  James Westra,  who is a stockholder  of Hutchins,  Wheeler & Dittmar,  A
Professional Corporation, beneficially owns 5,150 shares of the Company's Common
Stock.

                                      - 3 -
Item 6.  Indemnification of Directors and Officers

     Section 67 of  Chapter  156B of the  General  Laws of the  Commonwealth  of
Massachusetts provides as follows:

     "Section 67.  Indemnification of directors,  officers,  employees and other
agents of a  corporation,  and persons  who serve at its  request as  directors,
officers, employees or other agents of another organization, or who serve at its
request in any  capacity  with  respect to any  employee  benefit  plan,  may be
provided by it to whatever extent shall be specified in or authorized by (i) the
articles of organization or (ii) a by-law adopted by the stockholders or (iii) a
vote  adopted by the  holders of a majority  of the shares of stock  entitled to
vote on the election of  directors.  Except as the articles of  organization  or
by-laws  otherwise  require,  indemnification  of any persons referred to in the
preceding  sentence who are not directors of the  corporation may be provided by
it to the extent authorized by the directors.  Such  indemnification may include
payment by the corporation of expenses incurred in defending a civil or criminal
action or  proceeding  in advance  of the final  disposition  of such  action or
proceeding,  upon receipt of an undertaking  by the person  indemnified to repay
such payment if he shall be  adjudicated  to be not entitled to  indemnification
under this section which  undertaking may be accepted  without  reference to the
financial ability of such person to make repayment. Any such indemnification may
be  provided  although  the person to be  indemnified  is no longer an  officer,
director,  employee or agent of the corporation or of such other organization or
no longer serves with respect to any such employee benefit plan.

     No  indemnification  shall 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 or to the extent that such matter relates to service
with  respect  to an  employee  benefit  plan,  in  the  best  interests  of the
participants or beneficiaries of such employee benefit plan.

     The absence of any express  provision for  indemnification  shall not limit
any right of indemnification existing independently of this section.

     A corporation shall have power to purchase and maintain insurance on behalf
of any person who is or was a director,  officer, employee or other agent of the
corporation,  or is or was  serving  at the  request  of  the  corporation  as a
director,  officer,  employee  or other  agent of another  organization  or with
respect to any employee benefit plan,  against any liability  incurred by him in
any such  capacity,  or arising  out of his  status as such,  whether or not the
corporation would have the power to indemnify him against such liability."

     Article 6 of the  Restated  Articles of  Organization,  as amended,  of the
Company reads as follows:

                                      - 4 -
Article 6.

     "Other lawful provisions for the conduct and regulation of the business and
affairs of the  Corporation,  for its  voluntary  dissolution  or for  limiting,
defining or  regulating  the powers of the  Corporation,  or of its directors or
stockholders, or of any class of stockholders are as follows: [...]

     No Director of the  Corporation  shall be liable to the  Corporation or its
stockholders  for monetary  damages for breach of  fiduciary  duty as a Director
notwithstanding  any statutory  provision or other law imposing such  liability,
except for liability of a director (i) for any breach of the Director's  duty of
loyalty to the Corporation or its  stockholders,  (ii) for acts or omissions not
in good faith or which involve intentional  misconduct or a knowing violation of
law,  (iii) under Section 61 or 62 of Chapter 156 of the  Massachusetts  General
Laws, or (iv) for any  transaction  from which the Director  derived an improper
personal benefit."
 

         Article 7 of the Amended By-Laws of the Company provides as follows:

                                   Article 7.

                   Indemnification of Directors and Officers 

Section 7.1        Definitions
 
     "For purposes of this Article 7:

(a)  'Director/officer'  means any  person  who is  serving  or has  served as a
Director,  officer or employee of the  Corporation  appointed  or elected by the
Board of Directors or the  stockholders  of the  Corporation,  or any  Director,
officer  or  employee  of the  Corporation  who is  serving or has served at the
request of the Corporation as a Director, officer, trustee, principal,  partner,
employee or other agent of any other organization.

(b)  'Proceeding'  means any  action,  suit or  proceeding,  civil or  criminal,
brought  or  threatened  in or before  any court,  tribunal,  administrative  or
legislative body or agency.

(c) 'Expense' means any fine or penalty,  and any liability fixed by a judgment,
order, decree or award in a Proceeding, any amount reasonably paid in settlement
of a Proceeding and any  professional  fees and other  disbursements  reasonably
incurred in connection with a Proceeding.

Section 7.2       Right to Indemnification

     Except as limited by law or as  provided  in  Sections  7.3 and 7.4 of this
Article 7, each  Director/officer  (and his heirs and personal  representatives)

                                     - 6 -
shall be indemnified  by the  Corporation  against any Expense  incurred by such
Director/officer  in  connection  with  each  Proceeding  in  which he or she is
involved   as  a  result  of  his  or  her   serving  or  having   served  as  a
Director/officer.

Section 7.3       Indemnification Not Available

     No indemnification  shall be provided to a Director/officer with respect to
a Proceeding as to which it shall have been  adjudicated  that he or she did not
act in good  faith in the  reasonable  belief  that his or her action was in the
best interests of the Corporation.

Section 7.4       Compromise or Settlement

     In the event that a Proceeding  is  compromised  or settled so as to impose
any liability or obligation on a  Director/officer  or upon the Corporation,  no
indemnification  shall be provided as to said  Director/officer  with respect to
such Proceeding if such Director/officer shall have been adjudicated not to have
acted in good faith in the  reasonable  belief that his or her action was in the
best interests of the Corporation.

Section 7.5       Advances
 
     The Corporation shall pay sums on account of  indemnification in advance of
a final  disposition  of a  Proceeding  upon  receipt of an  undertaking  by the
Director/officer to repay such sums if it is subsequently established that he or
she is not entitled to indemnification  pursuant to Sections 7.3 and 7.4 hereof,
which  undertaking may be accepted without reference to the financial ability of
such person to make repayment.

Section 7.6       Not Exclusive
 
     Nothing in this Article 7 shall limit any lawful rights to  indemnification
existing independently of this Article 7.

Section 7.7       Insurance

     The  provisions of this Article 7 shall not limit the power of the Board of
Directors to authorize  the purchase and  maintenance  of insurance on behalf of
any  Director/officer  against any Expense whether or not the Corporation  would
have the power to indemnify  such  Director/officer  against such Expense  under
this Article 7."

Item 7.  Exemption from Registration Claimed

     Not Applicable.

                                      - 7 -
Item 8.  Exhibits
Number              Description
4.1                1982 Stock Option Plan (incorporated by reference to Exhibit 10.1 to the
                             Company's Registration Statement on Form S-1 (333-41139))

          4.2                1991 Stock Option Plan (incorporated by reference to Exhibit 10.2 to the
                             Company's Registration Statement on Form S-1 (333-41139))

          4.3                1993 Stock Option Plan for Non-Employee Directors (incorporated by
                             reference to Exhibit 10.3 to the Company's Registration Statement on
                             Form S-1 (333-41139))

          4.4                1997 Stock Option Plan (incorporated by reference to Exhibit 10.4 to the
                             Company's Registration Statement on Form S-1 (333-41139))

          4.5                The First Amendment to the 1997 Stock Option Plan filed herewith

          4.6                1997 Employee Stock Purchase Plan (incorporated by reference to
                             Exhibit 10.5 to the Company's Registration Statement on Form S-1
                             (333-41139))

          5.1                Opinion of Hutchins, Wheeler & Dittmar, A Professional Corporation

         23.1                Consent of Independent Public Accountants
 
         23.2                 Consent of Hutchins, Wheeler & Dittmar, A Professional Corporation
                              (included in Exhibit 5.1)
Item 9.  Undertakings

        The undersigned Registrant hereby undertakes the following:

        (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:

               (i)  To include any  prospectus  required by Section  10(a)(3) of
                    the Securities Act of 1933;

                                      - 8 -
(ii) To reflect  in the  prospectus  any facts or events  arising
                    after the effective date of the  registration  statement (or
                    the most recent  post-effective  amendment  thereof)  which,
                    individually  or in the  aggregate,  represent a fundamental
                    change  in the  information  set  forth in the  registration
                    statement;

               (iii)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.

Provided,  however, that paragraphs (a)(l)(i) and (a)(l)(ii) do not apply if the
information  required  to be  included in a  post-effective  amendment  by those
paragraphs is contained in periodic reports filed by the Registrant  pursuant to
Section  13 or Section  15(d) of the  Securities  Exchange  Act of 1934 that are
incorporated by reference 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.

(c)  The   undersigned   Registrant   hereby   undertakes,   that,   insofar  as
indemnification  for liabilities arising under the Securities Act of 1933 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

                                      - 9 -
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.

                                     - 10 -
SIGNATURES

     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 Chelmsford, Massachusetts on May 21, 1998.

                                        MERCURY COMPUTER SYSTEMS, INC.

                                        By /s/ James R. Bertelli 

                                          James R. Bertelli
                                          President

     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.
Signature                                      Title                                      Date
/s/ James R. Bertelli                             President, Chief Executive         May 21, 1998
James R. Bertelli                                  Officer and Director

/s/ G. Mead Wyman                                  Vice President, Chief             May 21, 1998
G. Mead Wyman                                      Financial Officer and
                                                   Treasurer

 
/s/ Gordon B. Baty                                 Director                          May 21, 1998
Gordon B. Baty

/s/ R. Schorr Berman                               Director                          May 21, 1998
R. Schorr Berman

/s/ Albert P. Belle Isle                           Director                          May 21, 1998
Albert P. Belle Isle

/s/ Sherman N. Mullin                              Director                          May 21, 1998
Sherman N. Mullin

/s/ Melvin Sallen                                  Director                          May 21, 1998
Melvin Sallen
- 11 -
SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    EXHIBITS

                                       to

                                    FORM S-8

                             REGISTRATION STATEMENT

                                      under

                           THE SECURITIES ACT OF 1933

                         MERCURY COMPUTER SYSTEMS, INC.
             (Exact name of registrant as specified in its charter)
Exhibit 4.5       First Amendment to the 1997 Stock Option Plan

                         MERCURY COMPUTER SYSTEMS, INC.

                             First Amendment to the
              Mercury Computer Systems, Inc. 1997 Stock Option Plan

     In accordance  with the  provisions  of Section 20 of the Mercury  Computer
Systems,  Inc.  1997  Stock  Option  Plan (the  "Plan"),  the Plan is amended as
follows:  

     1.  Section 2 of the Plan is hereby  amended  by  increasing  the number of
shares  subject to the Plan from Five Hundred  Seventy-Five  Thousand  (575,000)
shares to One Million Three Hundred Twenty-Five  Thousand  (1,325,000) shares of
the $.01 par value common stock of the Corporation.

     2. This  Amendment  shall take effect as of the date of its adoption by the
Mercury Computer  Systems,  Inc. Board of Directors and upon its approval by the
stockholders of Mercury Computer Systems, Inc. in accordance with the provisions
of Section 20 of the Plan.

     3.  Except  as  hereinabove  provided,  the  Plan is  hereby  ratified  and
confirmed in all respects.

                                        MERCURY COMPUTER SYSTEMS, INC.

                                        By:  /s/ Anthony J. Medaglia, Jr.
                                             Anthony J. Medaglia, Jr.
                                             Clerk

Adopted by the Board of Directors                    October 20, 1997

Adopted by the Stockholders                          December 18, 1997
Exhibit 5.1  Opinion of Hutchins, Wheeler & Dittmar, A Professional Corporation

                                        May 21, 1998

Mercury Computer Systems, Inc.
199 Riverneck Road
Chelmsford, MA 01824

Ladies and Gentlemen:

     We are general counsel to Mercury Computer  Systems,  Inc., a Massachusetts
corporation  (the  "Company"),  and as such  counsel  we are  familiar  with the
corporate  proceedings  taken in  connection  with the adoption of the Company's
1982 Stock  Option  Plan,  1991 Stock  Option  Plan,  1993 Stock Option Plan for
Non-Employee Directors,  1997 Stock Option Plan and 1997 Employee Stock Purchase
Plan  (collectively  the "Plans").  We are also  familiar with the  registration
statement  on Form S-8 to which a copy of this  opinion  will be  attached as an
exhibit.

     As such counsel,  we have  examined the  corporate  records of the Company,
including the Restated Articles of Organization, By-laws, stock records, minutes
of meetings of its Board of Directors and  stockholders and such other documents
as we have deemed necessary as a basis for the opinions herein expressed.

     Based upon the foregoing,  and having regard for such legal  considerations
as we deem relevant, we are of the opinion that:

     1. The Company is duly organized and validly existing under the laws of the
Commonwealth of Massachusetts;

     2. The Company has authorized  the issuance of 25,000,000  shares of common
stock  having a par value of $.01 per share and  1,000,000  shares of  preferred
stock having a par value of $.01 per share.

     3. The shares of common stock issuable  pursuant to the Plans, when sold in
accordance  with the terms  thereof,  will be  legally  issued,  fully  paid and
non-assessable.
Mercury Computer Systems, Inc.
May 21, 1998
Page 2

     We hereby  consent  to the  filing of this  opinion  as an  exhibit  to the
Registration  Statement on Form S-8 and to the reference to us under the caption
"Interests of Named Experts and Counsel" in the Registration Statement.

                                        Very truly yours,

                                        /s/Hutchins, Wheeler & Dittmar
                                        HUTCHINS, WHEELER & DITTMAR
                                        A Professional Corporation
Exhibit 23.1               Consent of Independent Public Accountants

CONSENT OF INDEPENDENT ACCOUNTANTS

     We consent to the incorporation by reference in the Registration  Statement
of Mercury  Computer  Systems,  Inc.  (the  "Company") on Form S-8 of our report
dated August 28, 1997, except for the information in the final paragraph of Note
F, as to which the date is December 12, 1997, on our audits of the  consolidated
financial  statements  of the Company as of June 30, 1996 and 1997,  and for the
three years in the period ended June 30,  1997,  which report is included in the
Company's registration statement on Form S-1 (File No. 333-41139) filed with the
Securities and Exchange Commission pursuant to the Securities Act of 1933.

                                        Coopers & Lybrand L.L.P.

                                        /s/Coopers & Lybrand L.L.P.
Boston, Massachusetts
May 21, 1998