MONOLITHIC POWER SYSTEMS INC — Director's Dealing 2010

May 3, 2010

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MONOLITHIC POWER SYSTEMS INC (MPWR)
CIK: 0001280452
Period of Report: 2010-04-30

Reporting Person: Sciammas Maurice (Sr. V.P.of Sales and Marketing)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-04-30	Common Stock	M	10000	$1.2	Acquired	80741	Direct
2010-04-30	Common Stock	S	10000	$25.2309	Disposed	70741	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2010-04-30	Incentive Stock Option (right to buy)	$1.2	M	10000	Disposed	2013-09-11	Common Stock (10000)	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	95934	Indirect
Common Stock	24671	Indirect
Common Stock	24671	Indirect

Footnotes

F1: In accordance with the reporting person's 10b5-1 trading plan.

F2: The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $25.10 to $25.32. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price

F3: Shares held by Sciammas Family Living Trust, Maurice Sciammas and Christina Sciammas, Trustees

F4: Shares held by Christina Sciammas 2004 Trust, Christina Sciammas and Maurice Sciammas, Trustees

F5: Shares held by Maurice Sciammas 2004 Trust, Maurice Sciammas and Christina Sciammas, Trustees