<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM ILLUMINA,
INC.'S BALANCE SHEETS AS OF DECEMBER 31, 1998, DECEMBER 31, 1999 AND MARCH 31,
2000 AND RELATED STATEMENTS OF OPERATIONS STOCKHOLDERS' EQUITY, AND CASH FLOWS
FOR THE PERIOD FROM APRIL 28, 1998 (INCEPTION) TO DECEMBER 31, 1998, FOR THE
YEAR ENDED DECEMBER 31, 1999 AND FOR THE THREE MONTHS ENDED MARCH 31, 2000 AND
IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<S> <C> <C> <C>
<PERIOD-TYPE> 8-MOS YEAR 3-MOS
<FISCAL-YEAR-END> DEC-31-1998 DEC-31-1999 DEC-31-2000
<PERIOD-START> APR-28-1998 JAN-01-1999 JAN-01-2000
<PERIOD-END> DEC-31-1998 DEC-31-1999 MAR-31-2000
<CASH> 8,233,729 21,164,114 15,067,452
<SECURITIES> 0 11,924,163 17,649,664
<RECEIVABLES> 0 49,818 22,701
<ALLOWANCES> 0 0 0
<INVENTORY> 0 0 0
<CURRENT-ASSETS> 8,408,249 33,493,045 33,487,535
<PP&E> 1,000 296,286 836,780
<DEPRECIATION> 0 (4,972) (34,749)
<TOTAL-ASSETS> 8,557,415 33,894,658 34,430,208
<CURRENT-LIABILITIES> 177,170 612,408 1,095,851
<BONDS> 0 0 0
0 0 0
9,397,998 37,397,998 37,397,998
<COMMON> 34,560 51,391 67,048
<OTHER-SE> (1,052,313) (5,417,139) (6,630,689)
<TOTAL-LIABILITY-AND-EQUITY> 8,557,415 33,894,658 34,430,208
<SALES> 0 0 0
<TOTAL-REVENUES> 0 474,026 83,205
<CGS> 0 0 0
<TOTAL-COSTS> 1,194,168 6,354,568 4,471,740
<OTHER-EXPENSES> 0 0 0
<LOSS-PROVISION> 0 0 0
<INTEREST-EXPENSE> 0 48,517 0
<INCOME-PRETAX> (1,145,620) (5,517,645) (3,900,853)
<INCOME-TAX> 0 0 0
<INCOME-CONTINUING> (1,145,620) (5,517,645) (3,900,853)
<DISCONTINUED> 0 0 0
<EXTRAORDINARY> 0 0 0
<CHANGES> 0 0 0
<NET-INCOME> (1,145,620) (5,517,645) (3,900,853)
<EPS-BASIC> (1.71) (3.91) (2.31)
<EPS-DILUTED> (1.71) (3.91) (2.31)
</TABLE>