X0305 4 2012-06-01 0000031462 ECOLAB INC ECL 0000902012 GATES WILLIAM H III ONE MICROSOFT WAY REDMOND WA 98052 1 1 See footnotes (2) and (3) 0001052192 CASCADE INVESTMENT LLC 2365 CARILLON POINT KIRKLAND WA 98033 1 See footnote (2) Common Stock 2012-06-01 4 P 0 383656.0000 61.8359 A 27385004.0000 I by Cascade Investment, L.L.C. This transaction was executed in multiple trades at prices ranging from $61.72 to $61.9550. The price set forth above reflects the weighted-average price per share. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transactions were effected. For purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (the "Act"), Mr. Gates, as the sole member of Cascade Investment, L.L.C. ("Cascade") and co-trustee of Bill & Melinda Gates Foundation Trust ("Trust"), may be deemed to beneficially own more than 10% of the common stock of the Issuer. Mr. Gates has no pecuniary interest in the shares held by the Trust. Neither the filing of this Form 4 nor any of its contents shall be deemed an admission that Mr. Gates and any other person or persons constitute a "group" under Section 13(d) and Mr. Gates expressly disclaims membership in a group. For purposes of Section 13(d) of the Act, Cascade may be deemed to be a member of a "group" that beneficially owns more than 10% of the common stock of the Issuer. Neither the filing of this Form 4 nor any of its contents shall be deemed an admission that Cascade and any other person or persons constitute a "group" under Section 13(d) or is otherwise subject to Section 16 of the Act and Cascade expressly disclaims membership in a group. /s/ Alan Heuberger, Attorney-in-fact for William H. Gates III 2012-06-05 /s/ Cascade Investment, L.L.C. by Alan Heuberger as attorney-in-fact for Michael Larson, Business Manager 2012-06-05