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: 2010-05-03

Reporting Person: Neely Rick (Sr. VP and CFO)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-05-03	Common Stock	M	8850	$8.41	Acquired	43405	Direct
2010-05-03	Common Stock	M	1843	$11.85	Acquired	45248	Direct
2010-05-03	Common Stock	S	10222	$24.3326	Disposed	35026	Direct
2010-05-03	Common Stock	S	471	$25.1159	Disposed	34555	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2010-05-03	Incentive Stock Option (right to buy)	$8.41	M	8850	Disposed	2015-09-22	Common Stock (8850)	Direct
2010-05-03	Non-Qualified Stock Option (right to buy)	$11.85	M	1843	Disposed	2013-10-26	Common Stock (1843)	Direct

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 $24.09 to $25.07. 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: 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 $25.0925 to $25.13. 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