X0303 4 2010-05-13 false 0001373671 Isilon Systems, Inc. ISLN 0001057881 VAN OPPEN PETER H 99 UNION STREET, SUITE 2001 SEATTLE WA 98101 true false false false Common Stock 2010-05-13 4 S false 68238 14.766 D 15000 D The "Amount" and "Price" reported in this Column 4 reflect the aggregate number and weighted-average price, respectively, of shares disposed. These shares were sold in multiple transactions at prices ranging from $14.70 to $15.04, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the SEC staff, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth herein. Keenan Conder, Attorney-in-Fact 2010-05-14