<PAGE> PAGE 1
000 A000000 02/28/99
000 C000000 0000862313
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 3.0.a
000 J000000 A
001 A000000 NUVEEN CAL MUNI MARKET OPPORTUNITY FUND, INC.
001 B000000 811-6081
001 C000000 3129178200
002 A000000 333 WEST WACKER DRIVE
002 B000000 CHICAGO
002 C000000 IL
002 D010000 60606
002 D020000 1286
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 N
007 B000000 0
007 C010100 1
007 C010200 2
007 C010300 3
007 C010400 4
007 C010500 5
007 C010600 6
007 C010700 7
007 C010800 8
007 C010900 9
007 C011000 10
008 A000001 NUVEEN ADVISORY CORP.
008 B000001 A
008 C000001 801-12353
008 D010001 CHICAGO
008 D020001 IL
008 D030001 60606
008 D040001 1286
011 A000001 JOHN NUVEEN & CO. INCORPORATED
011 B000001 8-13464
011 C010001 CHICAGO
011 C020001 IL
011 C030001 60606
011 C040001 1286
011 A000002 ALEX BROWN & SONS, INC.
011 B000002 8-31213
011 C010002 BALTIMORE
011 C020002 MD
011 C030002 21202
<PAGE> PAGE 2
011 A000003 SHEARSON, LEHMAN, HUTTON
011 B000003 8-12324
011 C010003 NEW YORK
011 C020003 NY
011 C030003 10281
011 A000004 SMITH BARNEY, HARRIS UPHAM & CO.
011 B000004 8-08177
011 C010004 NEW YORK
011 C020004 NY
011 C030004 10286
011 A000005 PAINE WEBBER INC.
011 B000005 8-16267
011 C010005 NEW YORK
011 C020005 NY
011 C030005 10019
011 A000006 BATEMAN EICHLER, HILL RICHARCHS, INC.
011 B000006 8-28366
011 C010006 LOS ANGELES
011 C020006 CA
011 C030006 90017
011 A000007 CROWELL, WEEDON & CO.
011 B000007 8-3710
011 C010007 LOS ANGELES
011 C020007 CA
011 C030007 90017
012 A000001 CHASE MANHATTAN BANK
012 B000001 85-10233
012 C010001 NEW YORK
012 C020001 NY
012 C030001 10003
013 A000001 ERNST & YOUNG
013 B010001 CHICAGO
013 B020001 IL
013 B030001 60611
014 A000001 JOHN NUVEEN & CO., INC.
014 B000001 8-13464
015 A000001 CHASE MANHATTAN BANK
015 B000001 C
015 C010001 NEW YORK
015 C020001 NY
015 C030001 10003
015 E010001 X
015 A000002 DELETE
015 A000003 BANK OF NEW YORK
015 B000003 S
015 C010003 NEW YORK
015 C020003 NY
015 C030003 10007
015 E010003 X
015 A000004 BANKERS TRUST COMPANY
015 B000004 S
<PAGE> PAGE 3
015 C010004 NEW YORK
015 C020004 NY
015 C030004 10015
015 E010004 X
015 A000005 DELETE
015 A000006 DELETE
015 A000007 NATIONSBANK OF NORTH CAROLINA NA
015 B000007 S
015 C010007 CHARLOTTE
015 C020007 NC
015 C030007 28255
015 E010007 X
018 000000 Y
019 A000000 Y
019 B000000 100
019 C000000 NUVEENFUND
020 C000001 0
020 C000002 0
020 C000003 0
020 C000004 0
020 C000005 0
020 C000006 0
020 C000007 0
020 C000008 0
020 C000009 0
020 C000010 0
021 000000 0
022 A000001 LEHMAN BROTHERS
022 B000001 13-2518466
022 C000001 4000
022 D000001 0
022 A000002 STONE & YOUNGBERG
022 B000002 94-1052545
022 C000002 3250
022 D000002 0
022 A000003 M.R. BEAL & COMPANY
022 B000003 13-3452090
022 C000003 0
022 D000003 3078
022 A000004 J.P. MORGAN SECURITIES
022 B000004 13-3224016
022 C000004 1989
022 D000004 300
022 A000005 BT ALEX. BROWN INC.
022 B000005 13-3311934
022 C000005 0
022 D000005 1903
022 A000006 MILLER & SCHROEDER
022 B000006 41-0901194
022 C000006 0
022 D000006 1544
<PAGE> PAGE 4
022 A000007 ADVEST, INC.
022 B000007 06-0501867
022 C000007 0
022 D000007 1028
022 A000008 MORGAN STANLEY
022 B000008 13-2655998
022 C000008 0
022 D000008 1000
022 A000009 GOLDMAN SACHS & CO.
022 B000009 13-5108880
022 C000009 0
022 D000009 998
022 A000010 PRAGER, MCCARTHY & SEALY
022 B000010 94-3057440
022 C000010 0
022 D000010 498
023 C000000 10626
023 D000000 11654
024 000000 N
025 D000001 0
025 D000002 0
025 D000003 0
025 D000004 0
025 D000005 0
025 D000006 0
025 D000007 0
025 D000008 0
026 A000000 N
026 B000000 N
026 C000000 N
026 D000000 Y
026 E000000 N
026 F000000 N
026 G010000 N
026 G020000 N
026 H000000 N
027 000000 N
028 A010000 0
028 A020000 0
028 A030000 0
028 A040000 0
028 B010000 0
028 B020000 0
028 B030000 0
028 B040000 0
028 C010000 0
028 C020000 0
028 C030000 0
028 C040000 0
028 D010000 0
028 D020000 0
<PAGE> PAGE 5
028 D030000 0
028 D040000 0
028 E010000 0
028 E020000 0
028 E030000 0
028 E040000 0
028 F010000 0
028 F020000 0
028 F030000 0
028 F040000 0
028 G010000 0
028 G020000 0
028 G030000 0
028 G040000 0
028 H000000 0
030 A000000 0
030 B000000 0.00
030 C000000 0.00
031 A000000 0
031 B000000 0
032 000000 0
033 000000 0
035 000000 0
036 B000000 0
038 000000 0
042 A000000 0
042 B000000 0
042 C000000 0
042 D000000 0
042 E000000 0
042 F000000 0
042 G000000 0
042 H000000 0
043 000000 0
044 000000 0
045 000000 Y
046 000000 N
047 000000 Y
048 000000 0.000
048 A010000 125000
048 A020000 0.650
048 B010000 125000
048 B020000 0.638
048 C010000 250000
048 C020000 0.625
048 D010000 500000
048 D020000 0.613
048 E010000 1000000
048 E020000 0.600
048 F010000 0
048 F020000 0.000
<PAGE> PAGE 6
048 G010000 0
048 G020000 0.000
048 H010000 0
048 H020000 0.000
048 I010000 0
048 I020000 0.000
048 J010000 0
048 J020000 0.000
048 K010000 2000000
048 K020000 0.588
049 000000 N
050 000000 N
051 000000 N
052 000000 N
053 A000000 N
054 A000000 Y
054 B000000 N
054 C000000 N
054 D000000 N
054 E000000 N
054 F000000 N
054 G000000 N
054 H000000 Y
054 I000000 N
054 J000000 Y
054 K000000 N
054 L000000 N
054 M000000 Y
054 N000000 N
054 O000000 Y
055 A000000 Y
055 B000000 N
056 000000 N
057 000000 N
058 A000000 N
059 000000 Y
060 A000000 Y
060 B000000 Y
061 000000 0
062 A000000 Y
062 B000000 0.0
062 C000000 0.0
062 D000000 0.0
062 E000000 0.0
062 F000000 0.0
062 G000000 0.0
062 H000000 0.0
062 I000000 0.0
062 J000000 0.0
062 K000000 0.0
062 L000000 0.0
<PAGE> PAGE 7
062 M000000 0.0
062 N000000 0.0
062 O000000 99.0
062 P000000 0.0
062 Q000000 0.0
062 R000000 0.0
063 A000000 0
063 B000000 9.1
064 A000000 Y
064 B000000 N
066 A000000 N
067 000000 N
068 A000000 N
068 B000000 N
069 000000 N
070 A010000 Y
070 A020000 N
070 B010000 N
070 B020000 N
070 C010000 Y
070 C020000 N
070 D010000 N
070 D020000 N
070 E010000 Y
070 E020000 N
070 F010000 N
070 F020000 N
070 G010000 Y
070 G020000 N
070 H010000 N
070 H020000 N
070 I010000 N
070 I020000 N
070 J010000 Y
070 J020000 N
070 K010000 N
070 K020000 N
070 L010000 N
070 L020000 N
070 M010000 N
070 M020000 N
070 N010000 Y
070 N020000 N
070 O010000 Y
070 O020000 N
070 P010000 N
070 P020000 N
070 Q010000 N
070 Q020000 N
070 R010000 N
070 R020000 N
<PAGE> PAGE 8
071 A000000 9326
071 B000000 9854
071 C000000 184653
071 D000000 5
072 A000000 6
072 B000000 5587
072 C000000 0
072 D000000 0
072 E000000 0
072 F000000 596
072 G000000 0
072 H000000 0
072 I000000 15
072 J000000 22
072 K000000 8
072 L000000 12
072 M000000 1
072 N000000 0
072 O000000 0
072 P000000 0
072 Q000000 0
072 R000000 8
072 S000000 1
072 T000000 0
072 U000000 0
072 V000000 0
072 W000000 91
072 X000000 754
072 Y000000 0
072 Z000000 4833
072AA000000 370
072BB000000 0
072CC010000 0
072CC020000 1240
072DD010000 4051
072DD020000 0
072EE000000 940
073 A010000 0.5070
073 A020000 0.0000
073 B000000 0.1176
073 C000000 0.0000
074 A000000 372
074 B000000 0
074 C000000 0
074 D000000 183056
074 E000000 0
074 F000000 0
074 G000000 0
074 H000000 0
074 I000000 0
074 J000000 0
<PAGE> PAGE 9
074 K000000 0
074 L000000 2425
074 M000000 20
074 N000000 185873
074 O000000 0
074 P000000 92
074 Q000000 0
074 R010000 0
074 R020000 0
074 R030000 0
074 R040000 783
074 S000000 55000
074 T000000 129998
074 U010000 8003
074 U020000 0
074 V010000 16.24
074 V020000 0.00
074 W000000 0.0000
074 X000000 955
074 Y000000 0
075 A000000 0
075 B000000 186207
076 000000 17.56
077 A000000 Y
077 C000000 Y
077 Q010000 Y
078 000000 N
080 C000000 0
081 B000000 0
082 B000000 0
083 B000000 0
084 B000000 0
086 A010000 27
086 A020000 468
086 B010000 0
086 B020000 0
086 C010000 0
086 C020000 0
086 D010000 0
086 D020000 0
086 E010000 0
086 E020000 0
086 F010000 0
086 F020000 0
087 A010000 COMMON STOCK
087 A020000 67062U107
087 A030000 NCO
088 A000000 N
088 B000000 N
088 C000000 N
088 D000000 Y
<PAGE> PAGE 10
SIGNATURE STEPHEN D. FOY
TITLE V.P. & CONTROLLER
<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> AUG-31-1999
<PERIOD-START> SEP-01-1998
<PERIOD-END> FEB-28-1999
<INVESTMENTS-AT-COST> 165458
<INVESTMENTS-AT-VALUE> 183056
<RECEIVABLES> 2425
<ASSETS-OTHER> 392
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 185873
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 875
<TOTAL-LIABILITIES> 875
<SENIOR-EQUITY> 55000
<PAID-IN-CAPITAL-COMMON> 111630
<SHARES-COMMON-STOCK> 8003
<SHARES-COMMON-PRIOR> 7977
<ACCUMULATED-NII-CURRENT> 402
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 368
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 17598
<NET-ASSETS> 184998
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 5587
<OTHER-INCOME> 0
<EXPENSES-NET> 754
<NET-INVESTMENT-INCOME> 4833
<REALIZED-GAINS-CURRENT> 370
<APPREC-INCREASE-CURRENT> (1240)
<NET-CHANGE-FROM-OPS> 3963
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 4051
<DISTRIBUTIONS-OF-GAINS> 940
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 0
<NUMBER-OF-SHARES-REDEEMED> 0
<SHARES-REINVESTED> 27
<NET-CHANGE-IN-ASSETS> (1434)
<ACCUMULATED-NII-PRIOR> 290
<ACCUMULATED-GAINS-PRIOR> 1143
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 596
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 754
<AVERAGE-NET-ASSETS> 186207
<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>