Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

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(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  Sciammas Maurice
 2. Date of Event Requiring Statement (Month/Day/Year)
04/25/2006		 3. Issuer Name and Ticker or Trading Symbol
MONOLITHIC POWER SYSTEMS INC [MPWR]
(Last)
(First)
(Middle)
983 UNIVERSITY AVENUE, BUILDING A		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
VP, Sales and Marketing
 5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

LOS GATOS, CA 95032		 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)		 2. Amount of Securities Beneficially Owned
(Instr. 4)		 3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)		 4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Common Stock 17,762 (1)
D
 
Common Stock 257,574
I
by Family Trust (2)
Common Stock 42,647
I
byC Sciammas 04 TRST (3)
Common Stock 42,647
I
byM Sciammas 04 Trst (4)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)		 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)		 6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Incentive Stock Option (right to buy) 07/15/2003(5) 07/17/2012 Common Stock 82,000 $ 1.2 D  
Incentive Stock Option (right to buy) 09/10/2004(6) 09/11/2013 Common Stock 60,000 $ 1.2 D  
Incentive Stock Option (right to buy) 01/26/2006(7) 01/26/2015 Common Stock 21,206 $ 7.77 D  
Incentive Stock Option (right to buy) 06/15/2006(8) 06/15/2015 Common Stock 20,317 $ 9.32 D  
Non-Qualified Stock Option (right to buy) 01/26/2006(7) 01/26/2015 Common Stock 2,794 $ 7.77 D  
Non-Qualified Stock Option (right to buy) 06/15/2006(8) 06/15/2015 Common Stock 79,683 $ 9.32 D  

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Sciammas Maurice
983 UNIVERSITY AVENUE, BUILDING A
LOS GATOS, CA 95032		       VP, Sales and Marketing  

Signatures

Maurice Sciammas 05/01/2006
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) Includes 15,000 shares of RSA granted on 2/7/06; 7500 shares vest on 2/17/07 and 7500 shares vest on 2/17/08 provided that the Purchaser continues to be a Service Provider on such dates.
(2) Shares held by Sciammas Family Living Trust, Maurice Sciammas and Christina Sciammas, Trustees
(3) Shares held by Christina Sciammas 2004 Trust, Christina Sciammas and Maurice Sciammas, Trustees
(4) Shares held by Maurice Sciammas 2004 Trust, Maurice Sciammas and Christina Sciammas, Trustees
(5) Total of 82,000 shares granted on 7/17/02, 25% exercisable on 7/15/03; the remaining shares vest at a rate of 1/48 per month thereafter.
(6) Total of 60,000 shares granted on 9/11/03, 25% exercisable on 9/10/04; the remaining shares vest at a rate of 1/48 per month thereafter.
(7) Total of 24,000 shares granted on 1/26/05, 25% exercisable on 1/26/06; the remaining shares vest at a rate of 1/48 per month thereafter.
(8) Total of 100,000 shares granted on 6/15/05, 25% exercisable on 6/15/06; the remaining shares vest at a rate of 1/48 per month thereafter.

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