X0304 4 2011-08-23 0000031462 ECOLAB INC ECL 0000902012 GATES WILLIAM H III ONE MICROSOFT WAY REDMOND WA 98052 1 1 See Footnotes 1,2 0001052192 CASCADE INVESTMENT LLC 2365 CARILLON POINT KIRKLAND WA 98033 1 See Remarks Common Stock 2011-08-23 4 P 0 930162.0000 48.8192 A 19759748.0000 I by Cascade Investment, L.L.C. Common Stock 2011-08-23 4 P 0 472290.0000 48.4935 A 20232038.0000 I by Cascade Investment, L.L.C. Common Stock 2011-08-23 4 P 0 381034.0000 47.4572 A 20613072.0000 I by Cascade Investment, L.L.C. This transaction was executed in multiple trades at prices ranging from $48.65 to $49.00. 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. Mr. Gates may be deemed to be the beneficial owner of more than 10% of Ecolab Inc.'s common stock for purposes of Section 13(d) of the Securities Exchange Act of 1934 (the "Act") and therefore subject to Section 16 of the Act. For purposes of Rule 16a-1(a)(2) under the Act, however, Mr. Gates is the beneficial owner of only the securities held by Cascade Investment, L.L.C. and Mr. Gates disclaims beneficial ownership of any Ecolab Inc. common stock held by any other person. Both reporting persons disclaim membership in a "group" with one another or with any other person as that term is used in Section 13(d) of the Act, and the filing of this Form 4 shall not be deemed an admission that either reporting person is a member of such a group. This transaction was executed in multiple trades at prices ranging from $47.65 to $48.645. 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. This transaction was executed in multiple trades at prices ranging from $46.65 to $47.645. 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. /s/ Alan Heuberger, Attorney-in-fact for William H. Gates III 2011-08-25 /s/ Cascade Investment, L.L.C. by Alan Heuberger as attorney-in-fact for Michael Larson, Business Manager 2011-08-25