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                                                  OMB Number           3235-0287
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                     U.S. SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                     FORM 4

                  STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

    Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934,
       Section 17(a) of the Public Utility Holding Company Act of 1935 or
               Section 30(f) of the Investment Company Act of 1940

[  ] Check this box if no longer subject of Section 16. Form 4 or Form 5
     obligations may continue. See Instruction 1(b).

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1. Name and Address of Reporting Person

      Chasen, Steven
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   (Last)               (First)                 (Middle)

      76 Country Club Circle
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                                    (Street)

      Pembroke, MA  02359
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   (City)               (State)                 (Zip)


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2. Issuer Name and Ticker or Trading Symbol


      Mercury Computer Systems, Inc. ("MRCY")
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3. IRS or Social Security Number of Reporting Person (Voluntary)


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4. Statement for Month/Year

      December 2000
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5. If Amendment, Date of Original (Month/Year)


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6. Relationship of Reporting Person to Issuer
   (Check all applicable)

   [   ]   Director                             [   ]   10% Owner
   [ X ]   Officer (give title below)           [   ]   Other (specify below)


        Senior Vice President and General Manager, Operations
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7.  Individual or Joint/Group Filing (Check Applicable Line)
   [X  ]   Form filed by One Reporting Person

   [   ]   Form filed by More than One Reporting Person
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           Table I -- Non-Derivative Securities Acquired, Disposed of,
                             or Beneficially Owned
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6. 4. 5. Owner- Securities Acquired (A) or Amount of ship 3. Disposed of (D) Securities Form: 7. Transaction (Instr. 3, 4 and 5) Beneficially Direct Nature of 2. Code ------------------------------- Owned at End (D) or Indirect 1. Transaction (Instr. 8) (A) of Month Indirect Beneficial Title of Security Date ------------ Amount or Price (Instr. 3 (I) Ownership (Instr. 3) (mm/dd/yy) Code V (D) and 4) (Instr.4) (Instr. 4) - ------------------------------------------------------------------------------------------------------------------------------------ Common Stock 12/12/00 S 3,000 D 44.25 36,240 D - ------------------------------------------------------------------------------------------------------------------------------------ - ------------------------------------------------------------------------------------------------------------------------------------ ====================================================================================================================================
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly FORM 4 (continued) Table II -- Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities) ================================================================================
9. 10. Number Owner- of ship 2. Deriv- of Conver- 5. 7. ative Deriv- 11. sion Number of Title and Amount Secur- ative Nature of Derivative 6. of Underlying 8. ities Secur- of Exer- 4. Securities Date Securities Price Bene- ity: In- cise 3. Trans- Acquired (A) Exercisable and (Instr. 3 and 4) of ficially Direct direct Price Trans- action or Disposed Expiration Date ---------------- Deriv- Owned (D) or Bene- 1. of action Code of(D) (Month/Day/Year) Amount ative at End In- ficial Title of Deriv- Date (Instr. (Instr. 3, ---------------- or Secur- of direct Owner- Derivative ative (Month/ 8) 4 and 5) Date Expira- Number ity Month (I) ship Security Secur- Day/ ------ ------------ Exer- tion of (Instr. (Instr. (Instr. (Instr. (Instr. 3) ity Year) Code V (A) (D) cisable Date Title Shares 5) 4) 4) 4) - ------------------------------------------------------------------------------------------------------------------------------------ - ------------------------------------------------------------------------------------------------------------------------------------ Stock Option (Right to Buy) $2.00 (1) 7/30/06 Common D - ------------------------------------------------------------------------------------------------------------------------------------ Stock Option (Right to Buy) $4.00 (2) 9/19/06 Common D - ----------------------------------------------------------------------------------------------------------------------------------- Stock Option (Right to Buy) $7.625 (3) 9/28/08 Common D ==================================================================================================================================== Explanation of Responses: (1) The option became exercisable as to 720 shares on July 30, 1999, and becomes exercisable as to an additional 720 shares on each of July 30, 2001 and July 30, 2002. (2) The option became exercisable as to 12,500 shares on each of October 20, 1999 and October 20, 2000 and becomes exercisable as to an additional 12,500 shares on October 20, 2001. (3) The option became exercisable as to 400 shares on each of September 28, 1999 and September 28, 2000 and becomes exercisable as to an additional 400 shares on each of September 28, 2001, September 28, 2002 and September 20, 2003.
/s/Steven Chasen January 9, 2001 - --------------------------------------------- ----------------------- **Signature of Reporting Person Date ** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a). Note: File three copies of this Form, one of which must be manually signed. If space provided is insufficient, see Instruction 6 for procedures. Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.