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: SMITH JOHN ALEXANDER (Group VP, ASG)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-03-04	Common Stock	M	6000	$29.93	Acquired	6000	Direct
2011-03-04	Common Stock	S	6000	$31.90	Disposed	0	Direct
2011-03-04	Common Stock	M	2250	—	Acquired	2250	Direct
2011-03-04	Common Stock	M	1666	—	Acquired	3916	Direct
2011-03-04	Common Stock	F	1244	$32.05	Disposed	2672	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-03-04	Stock Option (Right to Buy)	$29.93	M	6000	Disposed	2014-01-06	Common Stock (6000)	Direct
2011-03-04	Restricted Stock Unit	$	M	2250	Disposed		Common Stock (2250)	Direct
2011-03-04	Restricted Stock Unit	$	M	1666	Disposed		Common Stock (1666)	Direct

Footnotes

F1: Each restricted stock unit represents the contingent right to receive one share of common stock of MKS Instruments, Inc.

F2: This transaction was effected pursuant to a Rule 10b5-1 trading plan previously adopted by the reporting person.

F3: 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.

F4: The RSUs vest in equal annual installments over three years.