December 14, 2006

VIA EDGAR AND FACSIMILE
Securities and Exchange Commission
Division of Corporation Finance
100 F Street, N.E.
Washington, D.C. 20549
Attention:        Ms. Barbara C. Jacobs
                  Ms. Rebekah Toton

         RE:      ISILON SYSTEMS, INC.
                  REGISTRATION STATEMENT ON FORM S-1
                  FILE NO. 333-137078

ACCELERATION REQUEST

         REQUESTED DATE:   DECEMBER 14, 2006
         REQUESTED TIME:   2:00 PM EASTERN TIME

Mesdames:

      Pursuant to Rule 461 under the Securities Act of 1933, as amended, Isilon
Systems, Inc. (the "Company") hereby requests that the above-referenced
Registration Statement on Form S-1 (File No. 333-137078) be declared effective
at the "Requested Date" and "Requested Time" set forth above or as soon
thereafter as practicable or at such later time as the Company may request by
telephone to the Commission. The Company also requests that you withdraw its
acceleration request dated December 11, 2006. This letter supersedes the
December 11, 2006 acceleration request. The Company hereby authorizes both Craig
Sherman and Mark J. Handfelt of Wilson Sonsini Goodrich & Rosati, P.C., counsel
for the Company, to make such requests on our behalf.

      Ms. Rebekah Toton of the Securities and Exchange Commission has confirmed
that it is not necessary for the Company to comply with the 48-hour advance
notice requirement promulgated by Rule 15c2-8 under the Securities Exchange Act
of 1934, as the request for acceleration had previously been made on December
11, 2006.

      In connection with the acceleration request, the Company hereby
acknowledges that:

            -     Should the Commission or the Staff, acting pursuant to
                  delegated authority, declare the filing effective, it does not
                  foreclose the Commission from taking any action with respect
                  to the filing;

            -     The action of the Commission or the Staff, acting pursuant to
                  delegated authority, in declaring the filing effective, does
                  not relieve the Company from its full responsibility for the
                  adequacy and accuracy of the disclosure in the filing; and

            -     The Company may not assert Staff comments and the declaration
                  of effectiveness as a defense in any proceeding initiated by
                  the Commission or any person under the federal securities laws
                  of the United States.

                                          Sincerely,

                                          ISILON SYSTEMS, INC.

                                          By:      /s/ Steven Goldman
                                              ---------------------------------
                                                Steven Goldman
                                                Chief Executive Officer



cc:      Douglas Choi
         ISILON SYSTEMS, INC.

         Craig Sherman
         Mark J. Handfelt
         WILSON SONSINI GOODRICH & ROSATI, PROFESSIONAL CORPORATION

         Laird H. Simons, III, Esq.
         Jeffrey R. Vetter, Esq.
         FENWICK & WEST LLP