EXHIBIT 99.1 CERTIFICATION UNDER SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 Jay T. Flatley and Timothy M. Kish hereby certify that: 1. They are the Chief Executive Officer and Chief Financial Officer, respectively, of Illumina, Inc. 2. The Form 10-Q report of Illumina, Inc. that this certification accompanies fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934. 3. The information contained in the Form 10-Q report of Illumina, Inc. that this certification accompanies fairly presents, in all material respects, the financial condition and results of operations of Illumina, Inc. Dated: November 13, 2002 By: /s/ JAY T. FLATLEY ------------------------------------- Jay T. Flatley President and Chief Executive Officer By: /s/ TIMOTHY M. KISH ------------------------------------- Timothy M. Kish Chief Financial Officer