MKS INC — Director's Dealing 2010

Jan 8, 2010

SEC Form 3 — Initial Statement of Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2010-01-01

Reporting Person: BAGSHAW SETH H (Vice President, CFO)

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	11482	Direct

Holdings (Derivative)

Security	Exercise Price	Expiration	Underlying	Shares	Ownership
Restricted Stock Unit	$		Common Stock (13800)		Direct

Footnotes

F1: RSU vests 100% three years after grant date. As such, 4,200 RSUs will vest on March 5, 2010, 4,200 RSUs will vest on March 28, 2008 and 5,400 RSUs will vest on May 26, 2012.

F2: RSU vests 100% three years after grant date.

F3: Each restricted stock unit represents the contingent right to receive one share of common stock of MKS Instruments, Inc.