
<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONSOLIDATED CONDENSED FINANCIAL STATEMENTS OF ONEOK, INC. FOR THE SIX MONTHS
ENDED JUNE 30, 2000, AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000

<S>                             <C>
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-2000
<PERIOD-START>                             JAN-01-2000
<PERIOD-END>                               JUN-30-2000
<CASH>                                           7,137
<SECURITIES>                                         0
<RECEIVABLES>                                  841,290
<ALLOWANCES>                                         0
<INVENTORY>                                    161,018
<CURRENT-ASSETS>                             1,786,863
<PP&E>                                       3,980,877
<DEPRECIATION>                               1,061,365
<TOTAL-ASSETS>                               5,372,104
<CURRENT-LIABILITIES>                        1,869,891
<BONDS>                                      1,357,869
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                        199
<COMMON>                                           316
<OTHER-SE>                                   1,195,120
<TOTAL-LIABILITY-AND-EQUITY>                 5,372,104
<SALES>                                      2,211,079
<TOTAL-REVENUES>                             2,211,079
<CGS>                                        1,578,529
<TOTAL-COSTS>                                2,026,390
<OTHER-EXPENSES>                                     0
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                              50,328
<INCOME-PRETAX>                                146,125
<INCOME-TAX>                                    58,056
<INCOME-CONTINUING>                             88,069
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                        2,115
<NET-INCOME>                                    90,184
<EPS-BASIC>                                       2.45
<EPS-DILUTED>                                     1.83


</TABLE>
