MKS INC — Director's Dealing 2011

Mar 7, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2011-03-04

Reporting Person: BERLINGHIERI LEO (Director, President and CEO)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-03-04	Common Stock	M	50000	$14.72	Acquired	55013	Direct
2011-03-05	Common Stock	S	50000	$32.023	Disposed	5013	Direct
2011-03-04	Common Stock	M	14624	—	Acquired	19637	Direct
2011-03-04	Common Stock	M	10833	—	Acquired	30470	Direct
2011-03-04	Common Stock	F	10629	$32.05	Disposed	19841	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-03-04	Stock Option (Right to Buy)	$14.72	M	50000	Disposed	2014-07-30	Common Stock (50000)	Direct
2011-03-04	Restricted Stock Unit	$	M	14624	Disposed		Common Stock (14624)	Direct
2011-03-04	Restricted Stock Unit	$	M	10833	Disposed		Common Stock (10833)	Direct

Footnotes

F1: This transaction was executed in multiple trades at prices ranging from $30.00 to $30.08. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide, upon request, the full information regarding the number of shares and prices at which the transaction was effected.

F2: Each restricted stock unit represents the contingent right to receive one share of common stock of MKS Instruments, Inc.

F3: This transaction was effected pursuant to a Rule 10b5-1 trading plan previously adopted by the reporting person.

F4: 25% after first year, 6.25% each quarter thereafter - total 4 years.

F5: These RSUs are subject to the achievement of performance criteria determined in the first year of the grant and thereafter vests in equal annual installments over three years.

F6: The RSUs vest in equal annual installments over three years.