EMERSON ELECTRIC CO — Director's Dealing 2006

Apr 19, 2006

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2006-04-17

Reporting Person: EMERSON ELECTRIC CO (10% Owner)
Reporting Person: ASTEC AMERICA INC (10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2006-04-17	Common Stock	S	15000	$22.8708	Disposed	7311711	Indirect
2006-04-18	Common Stock	S	15000	$23.2776	Disposed	7296711	Indirect

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	1065182	Direct

Footnotes

F1: The sales were effected in multiple transactions, at varying prices, on April 17, 2006, as follows and as described in
Footnote 2 below: 300 shares at $22.57; 400 at $22.58; 300 at $22.59; 1,400 at $22.60; 300 at $22.61; 878 at $22.63; 300 at
$22.64; 100 at $22.65; 500 at $22.66; 200 at $22.67; 400 at $22.69; 400 at $22.70; 100 at $22.72; 500 at $22.73; 100 at
$22.74; 459 at $22.75; 100 at $22.76; 100 at $22.77; 200 at $22.84; 100 at $22.91; 340 at $22.92; 360 at $22.93; 300 at
$22.94; 527 at $22.95; 500 at $22.96; 400 at $22.97; and 200 at $22.99.

F2: This footnote sets forth additional detail with respect to the transactions described in Footnote 1, as follows: 400 shares
at $23.01; 700 at $23.02; 100 at $23.03; 100 at $23.04; 500 at $23.05; 200 at $23.09; 200 at $23.10; 336 at $23.11; 300 at
$23.12; 500 at $23.13; 300 at $23.14; 300 at $23.16; 100 at $23.18; 200 at $23.19; 200 at $23.20; 400 at $23.24; 100 at
$23.25; 100 at $23.31; 100 at $23.32; and 100 at $23.33. The weighted average sales price for these transactions was
$22.8708 per share.

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 sales were effected in multiple transactions, at varying prices, on April 18, 2006, as follows and as described in
Footnote 5 below: 200 shares at $22.62; 200 at $22.80; 400 at $22.87; 100 at $22.89; 100 at $22.90; 100 at $22.91; 200 at
$22.92; 100 at $22.93; 200 at $22.94; 300 at $22.95; 500 at $22.97; 200 at $23.04; 100 at $23.07; 400 at $23.08; 100 at
$23.09; 400 at $23.10; 200 at $23.12; 100 at $23.13; 500 at $23.14; 200 at $23.15; 200 at $23.16; 200 at $23.18; 200 at
$23.19; 100 at $23.22; 100 at $23.23; and 300 at $23.25.

F5: This footnote sets forth additional detail with respect to the transactions described in Footnote 4, as follows: 300 shares
at $23.26; 300 at $23.27; 200 at $23.28; 100 at $23.29; 300 at $23.31; 400 at $23.33; 400 at $23.34; 100 at $23.35; 500 at
$23.40; 200 at $23.41; 700 at $23.43; 300 at $23.44; 1,700 at $23.45; 900 at $23.46; 527 at $23.47; 400 at $23.48; 700 at
$23.49; 477 at $23.50; 400 at $23.51; 200 at $23.52; 100 at $23.53; and 96 at $23.54. The weighted average sales price for
these transactions was $23.2776 per share.

F6: The reported securities are owned directly by Emerson Electric Co.