WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.
<TABLE> <S> <C>
<ARTICLE> 6
<RESTATED>
<CIK> 0000882868
<NAME> NUVEEN TAX-FREE UNIT TRUST
<SERIES> Series 651
<NAME> PENNSYLVANIA INSURED TRUST
<NUMBER> 157
<MULTIPLIER> 1
<CURRENCY> U.S. DOLLARS
<FISCAL-YEAR-END> MAY-31-2000
<PERIOD-START> JUN-01-1999
<PERIOD-END> MAY-31-2000
<PERIOD-TYPE> YEAR
<EXCHANGE-RATE> 1
<INVESTMENTS-AT-COST> 5,348,530
<INVESTMENTS-AT-VALUE> 5,506,876
<RECEIVABLES> 144,018
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 5,650,894
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 91,006
<TOTAL-LIABILITIES> 91,006
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 0
<SHARES-COMMON-STOCK> 54,959
<SHARES-COMMON-PRIOR> 57,580
<ACCUMULATED-NII-CURRENT> 69,894
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 86,925
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 158,346
<NET-ASSETS> 5,559,888
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 351,465
<OTHER-INCOME> 0
<EXPENSES-NET> 7,956
<NET-INVESTMENT-INCOME> 343,509
<REALIZED-GAINS-CURRENT> 6,443
<APPREC-INCREASE-CURRENT> -249,952
<NET-CHANGE-FROM-OPS> 100,000
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 346,677
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 70,000
<NUMBER-OF-SHARES-REDEEMED> 15,041
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> -510,988
<ACCUMULATED-NII-PRIOR> 73,062
<ACCUMULATED-GAINS-PRIOR> 80,482
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 0
<AVERAGE-NET-ASSETS> 0
<PER-SHARE-NAV-BEGIN> 0
<PER-SHARE-NII> 0
<PER-SHARE-GAIN-APPREC> 0
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 0
<EXPENSE-RATIO> 0
[AVG-DEBT-OUTSTANDING] 0
[AVG-DEBT-PER-SHARE] 0
</TABLE>
