EXHIBIT 99.3


     CERTIFICATION OF CHIEF EXECUTIVE OFFICER PURSUANT TO SECTION 302 OF THE
                           SARBANES-OXLEY ACT OF 2002
                            (18 U.S.C. SECTION 1350)

     I, James E. Dauwalter, certify that:

     1. I have reviewed this Quarterly Report on Form 10-Q of Entegris, Inc.;

     2. Based on my knowledge, this quarterly report does not contain any untrue
statement of a material fact or omit to state a material fact necessary to make
the statements made, in light of the circumstances under which such statements
were made, not misleading with respect to the period covered by this quarterly
report;

     3. Based on my knowledge, the financial statements, and other financial
information included in this quarterly report, fairly present in all material
respects the financial condition, results of operations and cash flows of the
registrant as of, and for, the periods presented in this quarterly report;

     4. The registrant's other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-14 and 15d-14) for the registrant and have:

          (a) designed such disclosure controls and procedures to ensure that
     material information relating to the registrant, including its consolidated
     subsidiaries, is made known to us by others within those entities,
     particularly during the period in which this quarterly report is being
     prepared;

          (b) evaluated the effectiveness of the registrant's disclosure
     controls and procedures as of a date within 90 days prior to the filing
     date of this quarterly report (the "Evaluation Date"); and

          (c) presented in this quarterly report our conclusions about the
     effectiveness of the disclosure controls and procedures based on our
     evaluation as of the Evaluation Date;

     5. The registrant's other certifying officer and I have disclosed, based on
our most recent evaluation, to the registrant's auditors and the audit committee
of registrant's board of directors (or persons performing the equivalent
function):

          (a) all significant deficiencies in the design or operation of
     internal controls which could adversely affect the registrant's ability to
     record, process, summarize and report financial data and have identified
     for the registrant's auditors any material weaknesses in internal controls;
     and

          (b) any fraud, whether or not material, that involves management or
     other employees who have a significant role in the registrant's internal
     controls; and

     6. The registrant's other certifying officer and I have indicated in this
quarterly report whether there were significant changes in internal controls or
in other factors that could significantly affect internal controls subsequent to
the date of our most recent evaluation, including any corrective actions with
regard to significant deficiencies and material weaknesses.


Date: January 14, 2003

                                       /s/ James E. Dauwalter

                                       James E. Dauwalter
                                       President and Chief Executive Officer
                                       (Principal Executive Officer)