<PAGE> PAGE 1
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000 I000000 3.0.a
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001 A000000 NUVEEN MUNICIPAL MARKET OPPORTUNITY FUND, INC
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002 A000000 333 WEST WACKER DRIVE
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011 B000002 8-12321
011 C010002 NEW YORK
011 C020002 NY
011 C030002 10292
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<PAGE> PAGE 2
011 B000003 8-13464
011 C010003 CHICAGO
011 C020003 IL
011 C030003 60606
011 C040003 1286
011 A000004 PAINE WEBBER INCORPORATED
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<PAGE> PAGE 3
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<PAGE> PAGE 4
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<PAGE> PAGE 5
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<PAGE> PAGE 6
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<PAGE> PAGE 7
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<PAGE> PAGE 8
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<PAGE> PAGE 9
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<PAGE> PAGE 10
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SIGNATURE STEPHEN D. FOY
TITLE V.P. & CONTROLLER
WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
This schedule contains Summary Financial Information extracted from the Form
N-SAR and the Financial Statements and is qualified in its entirety by
references to such documents.
</LEGEND>
<MULTIPLIER> 1000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> OCT-31-1999
<PERIOD-START> NOV-01-1998
<PERIOD-END> APR-30-1999
<INVESTMENTS-AT-COST> 920267
<INVESTMENTS-AT-VALUE> 995104
<RECEIVABLES> 20162
<ASSETS-OTHER> 1514
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<TOTAL-ASSETS> 1016780
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<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 4948
<TOTAL-LIABILITIES> 4948
<SENIOR-EQUITY> 300000
<PAID-IN-CAPITAL-COMMON> 633704
<SHARES-COMMON-STOCK> 45351
<SHARES-COMMON-PRIOR> 45195
<ACCUMULATED-NII-CURRENT> 1388
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<ACCUMULATED-NET-GAINS> 1903
<OVERDISTRIBUTION-GAINS> 0
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<INTEREST-INCOME> 31688
<OTHER-INCOME> 0
<EXPENSES-NET> 3872
<NET-INVESTMENT-INCOME> 27816
<REALIZED-GAINS-CURRENT> 1947
<APPREC-INCREASE-CURRENT> (13495)
<NET-CHANGE-FROM-OPS> 16268
<EQUALIZATION> 0
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<DISTRIBUTIONS-OF-GAINS> 674
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 0
<NUMBER-OF-SHARES-REDEEMED> 0
<SHARES-REINVESTED> 156
<NET-CHANGE-IN-ASSETS> (9375)
<ACCUMULATED-NII-PRIOR> 924
<ACCUMULATED-GAINS-PRIOR> 795
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 3141
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<GROSS-EXPENSE> 3872
<AVERAGE-NET-ASSETS> 1016556
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<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 0
<EXPENSE-RATIO> 0
[AVG-DEBT-OUTSTANDING] 0
[AVG-DEBT-PER-SHARE] 0
</TABLE>
