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  **UNITED STATES SECURITIES AND EXCHANGE COMMISSION****Washington, D.C. 20549** **FORM 10-Q/A**(Amendment No. 1)   þ **QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THESECURITIES EXCHANGE ACT OF 1934******For the quarterly period ended March 31, 2006******OR**   o **TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THESECURITIES EXCHANGE ACT OF 1934****Commission File Number 0-11250****DIONEX CORPORATION**(Exact name of registrant as specified in its charter)   Delaware 94-2647429   (State or other jurisdiction of (I.R.S. Employerincorporation or organization) Identification No.)   1228 Titan Way, Sunnyvale, California 94085   (Address of principal executive offices) (Zip Code)Registrant’s telephone number, including area code (408) 737-0700Indicate by check mark whether the registrant(1) has filed all reports required to be filed bySection 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or forsuch shorter period that the registrant was required to file such reports), and (2) has beensubject to such filing requirements for the past 90 days.YES þ NO oIndicate by check mark whether the registrant is a large accelerated filer, an accelerated filer,or a non-accelerated filer. See definition of “accelerated filer and large accelerated filer” inRule 12b-2 of the Exchange Act. (Check one):     Large accelerated filer o Accelerated filer þ Non-accelerated filer oIndicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of theExchange Act). Yes o No þIndicate the number of shares outstanding of each of the issuer’s classes of common stock, as ofMay 9, 2006:    CLASS  NUMBER OF SHARESCommon Stock  19,991,771  
 

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PART II. OTHER INFORMATIONItem 6. EXHIBITSSIGNATURESExhibit IndexEXHIBIT 31.1EXHIBIT 31.2

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EXPLANATORY NOTEThis Amendment No. 1 on Form 10-Q/A (this “Amendment”) amends the Company’s Quarterly Report onForm 10-Q for the third quarter ended March 31, 2006, originally filed on May 10, 2006 (the“Original Filing”). The Company is filing this Amendment solely in order to re-file Exhibit 31.1,Certification of Chief Executive Officer, and Exhibit 31.2, Certification of Chief FinancialOfficer (the “Certifications”), both of which include certifications in paragraph 4(b) related tointernal control over financial reporting that were inadvertently omitted from the Certificationsincluded in the Original Filing. Except for the additional paragraphs and the signatures as oftoday’s filing date, the Certifications have not changed in any respect from the Certificationsincluded in the Original Filing. This Form 10-Q/A does not modify or update any other exhibits ordisclosures presented in the Original Filing.PART II. OTHER INFORMATION**Item 6. EXHIBITS**   **Exhibit**  **Number** **Description****31.1** **Certification of Chief Executive Officer Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002**   **31.2** **Certification of Chief Financial Officer Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002**
 

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SIGNATURESPURSUANT TO THE REQUIREMENTS OF THE SECURITIES EXCHANGE ACT OF 1934, THE REGISTRANT HAS DULY CAUSEDTHIS AMENDED REPORT TO BE SIGNED ON ITS BEHALF BY THE UNDERSIGNED THEREUNTO DULY AUTHORIZED.         DIONEX CORPORATION    (Registrant)         Date: June 6, 2006 By: /s/ Lukas Braunschweiler             Lukas Braunschweiler      President, Chief Executive Officer and Director           By: /s/ Craig A. McCollam             Craig A. McCollam      Vice President, and Chief Financial Officer  
 

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Exhibit Index   31.1 Certification of Chief Executive Officer Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.   31.2 Certification of Chief Financial Officer Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.