EMERSON ELECTRIC CO — Director's Dealing 2006

Feb 23, 2006

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2005-12-12

Reporting Person: EMERSON ELECTRIC CO (10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2005-12-12	Common Stock	G	200000	—	Disposed	8463389	Indirect
2006-02-21	Common Stock	S	24000	$22.9702	Disposed	8439389	Indirect
2006-02-22	Common Stock	S	64653	$22.7786	Disposed	8374736	Indirect

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	1065182	Direct

Footnotes

F1: Bona fide gift to the Emerson Charitable Trust not previously reported.

F2: Price is not applicable to acquisitions or dispositions resulting from bona fide gifts.

F3: The reported securities are owned directly by Astec America Inc. The Reporting Person is the ultimate parent company of
Astec America Inc.

F4: The Reporting Person gave a sell order to the broker to sell shares of MKS Instruments, Inc. common stock which resulted in
sales of 24,000 shares on February 21, 2006. In the discretion of the broker, the sale was effected in multiple
transactions, at varying prices, on February 21, 2006, as follows: 400 shares at $22.83; 100 at $22.85; 100 at $22.86; 200
at $22.87; 300 at $22.88; 400 at $22.89; 500 at $22.91; 1,000 at $22.92; 1,700 at $22.93; 2,300 at $22.94; 1,600 at $22.95;
1,500 at $22.96; 1,600 at $22.97; 2,500 at $22.98; 4,100 at $22.99; 2,000 at $23.00; 200 at $23.01; 1,000 at $23.02; 100 at
$23.03; 600 at $23.04; 1,600 at $23.05; and 200 at $23.06. The average sales price for these transactions was $22.9702 per
share.

F5: The Reporting Person gave a sell order to the broker to sell shares of MKS Instruments, Inc. common stock which resulted in
sales of 64,653 shares on February 22, 2006. In the discretion of the broker, the sale was effected in multiple
transactions, at varying prices, on February 22, 2006, as follows and as described in Footnote (6) below: 200 shares at
$22.08; 100 at $22.15; 100 at $22.20; 300 at $22.23; 200 at $22.28; 200 at $22.29; 311 at $22.30; 189 at $22.31; 400 at
$22.34; 200 at $22.38; 100 at $22.40; 501 at $22.42; 520 at $22.43; 480 at $22.45; 200 at $22.46; 100 at $22.48; 300 at
$22.52; 99 at $22.53; 200 at $22.54; 300 at $22.55; 400 at $22.58; 200 at $22.59; 500 at $22.60; 100 at $22.61; 500 at
$22.63; 100 at $22.64; 400 at $22.66; 600 at $22.70; and 300 at $22.71.

F6: This footnote sets forth additional detail with respect to the transactions described in Footnote (5), as follows: 700 shares
at $22.72; 1,400 at $22.73; 800 at $22.74; 800 at $22.75; 1,600 at $22.76; 3,082 at $22.77; 3,332 at $22.78; 5,844 at
$22.79; 10,152 at $22.80; 4,084 at $22.81; 4,400 at $22.82; 3,200 at $22.83; 2,200 at $22.84; 1,200 at $22.85; 1,500 at
$22.86; 1,700 at $22.87; 4,010 at $22.88; 2,049 at $22.89; 1,400 at $22.90; 300 at $22.91; 500 at $22.92; 300 at $22.93; 300
at $22.94; 300 at $22.96; 200 at $22.98; 400 at $22.99; and 800 at $23.00. The average sales price for these transactions
was $22.7786 per share.

F7: The reported securities are owned directly by Emerson Electric Co.