
<TABLE> <S> <C>

<PAGE>

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

<S>                                       <C>
<PERIOD-TYPE>                              9-MOS
<FISCAL-YEAR-END>                          DEC-31-2000
<PERIOD-START>                             JAN-01-2000
<PERIOD-END>                               SEP-30-2000
<CASH>                                             137
<SECURITIES>                                         0
<RECEIVABLES>                                1,147,918
<ALLOWANCES>                                         0
<INVENTORY>                                    322,983
<CURRENT-ASSETS>                             2,405,842
<PP&E>                                       4,066,654
<DEPRECIATION>                               1,090,101
<TOTAL-ASSETS>                               6,346,951
<CURRENT-LIABILITIES>                        2,551,873
<BONDS>                                      1,348,955
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                        199
<COMMON>                                           316
<OTHER-SE>                                   1,187,189
<TOTAL-LIABILITY-AND-EQUITY>                 6,346,951
<SALES>                                      3,970,390
<TOTAL-REVENUES>                             3,970,390
<CGS>                                        3,379,272
<TOTAL-COSTS>                                3,736,620
<OTHER-EXPENSES>                                     0
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                              82,665
<INCOME-PRETAX>                                161,240
<INCOME-TAX>                                    63,085
<INCOME-CONTINUING>                             98,155
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                        2,115
<NET-INCOME>                                   100,270
<EPS-BASIC>                                       2.48
<EPS-DILUTED>                                     2.04


</TABLE>
