UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                   FORM 10-Q/A
                                (Amendment No. 1)

[X]   QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
      EXCHANGE ACT OF 1934

For the quarterly period ended June 30, 2005

[ ]   TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
      EXCHANGE ACT OF 1934

For the transition period from __________ to  __________

Commission file Number: 1-16239

                                   ATMI, Inc.
                                   ----------
             (Exact name of registrant as specified in its charter)

           Delaware                                     06-1481060
           --------                                     ----------
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
 incorporation or organization)

     7 Commerce Drive, Danbury, CT                             06810
     -----------------------------                             -----
 (Address of principal executive offices)                    (Zip Code)

                                  203-794-1100
              (Registrant's telephone number, including area code)

- --------------------------------------------------------------------------------

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.  Yes |X|  No |_|

Indicate by check mark whether the registrant is an accelerated filer (as
defined by Rule 12b-2 of the Act). Yes |X|   No |_|

Indicate by check mark whether the registrant is a shell company (as defined in
Rule 12b-2 of the Exchange Act) Yes |_|   No |X|

The number of shares outstanding of the registrant's common stock as of August
3, 2005 was 37,679,849.



                                EXPLANATORY NOTE

      This Amendment No. 1 on Form 10-Q/A (this "Amendment") amends the
Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2005 filed
on August 8, 2005 (the "Original Filing"). We have filed this Amendment solely
to include the information required by Part II, Item 4 - Submission of Matters
to a Vote of Security Holders. This information was inadvertently omitted from
the Original Filing. In addition, in connection with the filing of this
Amendment and pursuant to the rules of the Securities and Exchange Commission,
we are including with this Amendment certain currently dated certifications.

      Except as described above, no other changes have been made to the Original
Filing. This Amendment has not resulted in any changes to our previously
reported financial results. This Amendment continues to speak as of the date of
the Original Filing, and we have not updated the disclosures contained in this
Amendment to reflect any events that occurred at a date subsequent to the
Original Filing.



                                       1



PART II- OTHER INFORMATION

Item 4.    Submission of Matters to a Vote of Security Holders

      On May 24, 2005, the Company held its 2005 annual meeting of stockholders
at which the following actions were approved: (1) two Class II directors were
elected for a term expiring at the annual meeting of stockholders in 2008; and
(2) the appointment of Ernst & Young LLP as the Company's Independent Registered
Public Accounting Firm for the fiscal year ending December 31, 2005 was
ratified.

      The table below represents the votes tabulated for the election of the two
Class II directors:

         Director                          In Favor          Withheld
         --------                          --------          --------
         Mark A. Adley                    30,908,848         2,352,642
         Eugene G. Banucci, Ph.D.         32,745,327           516,163


      The table below represents the votes tabulated for the ratification of
Ernst & Young LLP as the Company's Independent Registered Public Accounting Firm
for the fiscal year ending December 31, 2005:

             Votes For                     Votes Against     Abstentions
             ---------                     -------------     -----------
             33,229,192                       12,653            19,645


Item 6.    Exhibits

(a)   Exhibits

      31.1     Certification of the Chief Executive Officer pursuant to Section
               302 of the Sarbanes-Oxley Act of 2002.

      31.2     Certification of the Chief Financial Officer pursuant to Section
               302 of the Sarbanes-Oxley Act of 2002.

      32       Certifications of the Chief Executive Officer and Chief Financial
               Officer pursuant to Section 906 of the Sarbanes-Oxley Act of
               2002.



                                       2



                                   SIGNATURES

      Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.

                                      ATMI, Inc.

October 24, 2005

                                      By /s/ Douglas A. Neugold
                                        -------------------------------------
                                        Douglas A. Neugold
                                        President and Chief Executive Officer


                                      By /s/ Daniel P. Sharkey
                                        -------------------------------------
                                        Daniel P. Sharkey
                                        Vice President, Chief Financial Officer
                                        and Treasurer (Chief Accounting Officer)