EMERSON ELECTRIC CO — Director's Dealing 2006

May 17, 2006

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MKS INSTRUMENTS INC (MKSI)
CIK: 0001049502
Period of Report: 2006-05-15

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
2006-05-15	Common Stock	S	121100	$22.1649	Disposed	6694291	Indirect
2006-05-16	Common Stock	S	57000	$22.0577	Disposed	6637291	Indirect

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	1065182	Direct

Footnotes

F1: The sales were effected in multiple transactions, at varying prices, on May 15, 2006, as follows and as described in
Footnotes 2 and 3 below: 100 shares at $21.45; 100 at $21.46; 200 at $21.47; 500 at $21.49; 100 at $21.53; 100 at $21.55;
200 at $21.57; 200 at $21.58; 200 at $21.59; 100 at $21.60; 100 at $21.62; 100 at $21.63; 200 at $21.64; 200 at $21.65; 100
at $21.67; 100 at $21.71; 100 at $21.72; 100 at $21.73; 300 at $21.75; 200 at $21.76; 300 at $21.77; 200 at $21.78; 100 at
$21.79; 500 at $21.80; 700 at $21.81; 100 at $21.82; 200 at $21.83; 400 at $21.84; 400 at $21.85; 300 at $21.87; and 500 at
$21.88.

F2: This footnote sets forth additional detail with respect to the transactions described in Footnote 1, as follows: 100 shares
at $21.90; 500 at $21.91; 200 at $21.92; 500 at $21.93; 100 at $21.94; 800 at $21.95; 1,901 at $21.96; 2,199 at $21.97;
3,016 at $21.98; 3,282 at $21.99; 5,802 at $22.00; 4,101 at $22.01; 1,900 at $22.02; 3,300 at $22.03; 5,417 at $22.04; 1,737
at $22.05; 2,645 at $22.06; 3,100 at $22.07; 1,700 at $22.08; 860 at $22.09; 2,500 at $22.10; 2,340 at $22.11; 1,700 at
$22.12; 700 at $22.13; 800 at $22.14; 900 at $22.15; 800 at $22.16; 1,000 at $22.17; 1,535 at $22.18; 1,865 at $22.19; 2,900
at $22.20; 2,000 at $22.21; 602 at $22.22; 1,600 at $22.23; 1,798 at $22.24; 3,100 at $22.25; 4,800 at $22.26; 2,300 at
$22.27; 2,800 at $22.28; 3,700 at $22.29; and 1,603 at $22.30.

F3: This footnote sets forth additional detail with respect to the transactions described in Footnote 1, as follows: 897 shares
at $22.31; 1,139 at $22.32; 2,400 at $22.33; 500 at $22.34; 1,000 at $22.35; 3,000 at $22.36; 2,954 at $22.37; 1,607 at
$22.38; 1,800 at $22.39; 800 at $22.40; 700 at $22.41; 300 at $22.42; 600 at $22.43; 1,800 at $22.44; 3,100 at $22.45; 900
at $22.46; 400 at $22.47; 11 at $22.48; 320 at $22.49; 700 at $22.50; 480 at $22.51; 789 at $22.52; 100 at $22.53; 800 at
$22.54; 500 at $22.55; 500 at $22.56; 400 at $22.57; 100 at $22.58; 200 at $22.60; 200 at $22.62; 100 at $22.63; 100 at
$22.64; and 400 at $22.65. The weighted average sales price for these transactions was $22.1649 per share.

F4: The reported securities are owned directly by Astec America Inc. The Reporting Person is the ultimate parent company of
Astec America Inc.

F5: The sales were effected in multiple transactions, at varying prices, on May 16, 2006, as follows and as described in Footnote
6 below: 200 shares at $21.83; 200 at $21.84; 100 at $21.85; 160 at $21.88; 300 at $21.89; 432 at $21.90; 591 at $21.91; 308
at $21.92; 963 at $21.93; 1,146 at $21.94; 874 at $21.95; 2,502 at $21.96; 3,300 at $21.97; 3,133 at $21.98; 1,000 at
$21.99; 2,407 at $22.00; 1,100 at $22.01; 1,012 at $22.02; 1,035 at $22.03; 4,693 at $22.04; 4,979 at $22.05; 3,815 at
$22.06; 3,648 at $22.07; 2,800 at $22.08; 2,300 at $22.09; and 2,400 at $22.10.

F6: This footnote sets forth additional detail with respect to the transactions described in Footnote 5, as follows: 200 shares
at $22.11; 900 at $22.12; 700 at $22.13; 700 at $22.14; 318 at $22.15; 200 at $22.16; 600 at $22.17; 118 at $22.18; 682 at
$22.19; 200 at $22.20; 200 at $22.21; 2,400 at $22.22; 400 at $22.23; 1,700 at $22.24; 1,384 at $22.25; and 900 at $22.26.
The weighted average sales price for these transactions was $22.0577 per share.

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