<PAGE> PAGE 1
000 B000000 08/31/98
000 C000000 0000765199
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 ML CALIFORNIA MUNICIPAL SERIES TRUST
001 B000000 811-4264
001 C000000 6092822800
002 A000000 P.O. BOX 9011
002 B000000 PRINCETON
002 C000000 NJ
002 D010000 08543
002 D020000 9011
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 Y
007 B000000 2
007 C010100 1
007 C020100 MERRILL LYNCH CALIFORNIA MUNICIPAL BOND FUND
007 C030100 N
007 C010200 2
007 C020200 ML CALIFORNIA INSURED MUNICIPAL BOND FUND
007 C030200 N
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 A00AA01 FUND ASSET MANAGEMENT, L.P.
008 B00AA01 A
008 C00AA01 801-12485
008 D01AA01 PRINCETON
008 D02AA01 NJ
008 D03AA01 08543
008 D04AA01 9011
011 A00AA01 MERRILL LYNCH FUNDS DISTRIBUTOR, INC.
011 B00AA01 8-14663
011 C01AA01 PRINCETON
011 C02AA01 NJ
011 C03AA01 08543
011 C04AA01 9011
012 A00AA01 FINANCIAL DATA SERVICES, INC.
<PAGE> PAGE 2
012 B00AA01 84-01339
012 C01AA01 JACKSONVILLE
012 C02AA01 FL
012 C03AA01 32246
012 C04AA01 6484
013 A00AA01 DELOITTE & TOUCHE LLP
013 B01AA01 PRINCETON
013 B02AA01 NJ
013 B03AA01 08540
014 A00AA01 MERRILL LYNCH, PIERCE, FENNER & SMITH INC.
014 B00AA01 8-7221
015 A00AA01 THE BANK OF NEW YORK
015 B00AA01 C
015 C01AA01 NEW YORK
015 C02AA01 NY
015 C03AA01 10286
015 E01AA01 X
015 A00AA02 BANKERS TRUST COMPANY
015 B00AA02 S
015 C01AA02 NEW YORK
015 C02AA02 NY
015 C03AA02 10006
015 E01AA02 X
015 A00AA03 CHASE MANHATTAN BANK, N.A.
015 B00AA03 S
015 C01AA03 NEW YORK
015 C02AA03 NY
015 C03AA03 10017
015 E01AA03 X
015 A00AA04 CUSTODIAL TRUST CO.
015 B00AA04 S
015 C01AA04 NEW YORK
015 C02AA04 NY
015 C03AA04 10167
015 E01AA04 X
015 A00AA05 MORGAN GUARANTEE TRUST CO.
015 B00AA05 S
015 C01AA05 NEW YORK
015 C02AA05 NY
015 C03AA05 10260
015 E01AA05 X
018 00AA00 Y
019 A00AA00 Y
019 B00AA00 209
019 C00AA00 MERRILLLYN
020 A000001 SMITH BARNEY INC.
020 B000001 13-1912900
020 C000001 5
020 A000002 BZW SECURITIES INC.
020 C000002 2
020 C000003 0
<PAGE> PAGE 3
020 C000004 0
020 C000005 0
020 C000006 0
020 C000007 0
020 C000008 0
020 C000009 0
020 C000010 0
021 000000 7
022 A000001 GOLDMAN, SACHS & CO.
022 B000001 13-5108880
022 C000001 167450
022 D000001 160170
022 A000002 LEHMAN BROTHERS INC.
022 B000002 13-2518466
022 C000002 105547
022 D000002 101828
022 A000003 SUTRO & CO. INCORPORATED
022 B000003 94-1704902
022 C000003 42507
022 D000003 125326
022 A000004 MORGAN (J.P.) SECURITIES INC.
022 B000004 13-3224016
022 C000004 93211
022 D000004 73609
022 A000005 MORGAN STANLEY & CO. INCORPORATED
022 B000005 13-2655998
022 C000005 114630
022 D000005 49940
022 A000006 SMITH BARNEY INC.
022 B000006 13-1912900
022 C000006 58740
022 D000006 47054
022 A000007 BEAR, STEARNS & CO. INC.
022 B000007 13-3299429
022 C000007 60950
022 D000007 32476
022 A000008 CIBC OPPENHEIMER CORP.
022 B000008 13-2798343
022 C000008 18264
022 D000008 52693
022 A000009 BT ALEX. BROWN INCORPORATED
022 B000009 13-3311934
022 C000009 41269
022 D000009 25932
022 A000010 PIPER JAFFRAY INC.
022 B000010 41-0953246
022 C000010 16933
022 D000010 47869
023 C000000 908848
023 D000000 926122
026 A000000 N
<PAGE> PAGE 4
026 B000000 Y
026 C000000 N
026 D000000 Y
026 E000000 N
026 F000000 N
026 G010000 N
026 G020000 N
026 H000000 N
027 000000 Y
045 00AA00 Y
046 00AA00 N
047 00AA00 Y
048 00AA00 0.000
048 A01AA00 500000
048 A02AA00 0.550
048 B01AA00 500000
048 B02AA00 0.525
048 C01AA00 0
048 C02AA00 0.000
048 D01AA00 0
048 D02AA00 0.000
048 E01AA00 0
048 E02AA00 0.000
048 F01AA00 0
048 F02AA00 0.000
048 G01AA00 0
048 G02AA00 0.000
048 H01AA00 0
048 H02AA00 0.000
048 I01AA00 0
048 I02AA00 0.000
048 J01AA00 0
048 J02AA00 0.000
048 K01AA00 1000000
048 K02AA00 0.500
054 A00AA00 Y
054 B00AA00 Y
054 C00AA00 N
054 D00AA00 N
054 E00AA00 N
054 F00AA00 N
054 G00AA00 N
054 H00AA00 Y
054 I00AA00 N
054 J00AA00 Y
054 K00AA00 N
054 L00AA00 N
054 M00AA00 Y
054 N00AA00 N
066 A00AA00 N
067 00AA00 N
<PAGE> PAGE 5
068 A00AA00 N
068 B00AA00 N
069 00AA00 N
077 A000000 Y
077 B000000 Y
078 000000 N
080 A00AA00 ICI MUTUAL INSURANCE CO.
080 C00AA00 1000
081 A00AA00 Y
081 B00AA00 130
082 A00AA00 N
082 B00AA00 0
083 A00AA00 N
083 B00AA00 0
084 A00AA00 N
084 B00AA00 0
085 A00AA00 Y
085 B00AA00 N
024 000100 N
028 A010100 4724
028 A020100 1027
028 A030100 0
028 A040100 7575
028 B010100 4805
028 B020100 997
028 B030100 0
028 B040100 9439
028 C010100 4300
028 C020100 1254
028 C030100 0
028 C040100 7655
028 D010100 4158
028 D020100 925
028 D030100 0
028 D040100 8517
028 E010100 4473
028 E020100 1210
028 E030100 0
028 E040100 7205
028 F010100 6444
028 F020100 963
028 F030100 0
028 F040100 7031
028 G010100 28904
028 G020100 6376
028 G030100 0
028 G040100 47422
028 H000100 4741
029 000100 Y
030 A000100 84
030 B000100 4.00
<PAGE> PAGE 6
030 C000100 0.00
031 A000100 9
031 B000100 0
032 000100 0
033 000100 75
034 000100 Y
035 000100 195
036 A000100 N
036 B000100 0
037 000100 N
038 000100 0
039 000100 N
040 000100 Y
041 000100 Y
042 A000100 0
042 B000100 0
042 C000100 100
042 D000100 0
042 E000100 0
042 F000100 0
042 G000100 0
042 H000100 0
043 000100 2037
044 000100 0
049 000100 N
050 000100 N
051 000100 N
052 000100 N
053 A000100 N
055 A000100 Y
055 B000100 N
056 000100 Y
057 000100 N
058 A000100 N
059 000100 Y
060 A000100 Y
060 B000100 Y
061 000100 1000
062 A000100 Y
062 B000100 0.0
062 C000100 0.0
062 D000100 0.0
062 E000100 1.9
062 F000100 0.0
062 G000100 0.0
062 H000100 0.0
062 I000100 0.0
062 J000100 0.0
062 K000100 0.0
062 L000100 0.0
062 M000100 0.0
<PAGE> PAGE 7
062 N000100 0.0
062 O000100 96.9
062 P000100 0.0
062 Q000100 0.0
062 R000100 0.0
063 A000100 0
063 B000100 19.7
064 A000100 Y
064 B000100 N
070 A010100 Y
070 A020100 N
070 B010100 N
070 B020100 N
070 C010100 Y
070 C020100 N
070 D010100 N
070 D020100 N
070 E010100 Y
070 E020100 Y
070 F010100 N
070 F020100 N
070 G010100 Y
070 G020100 N
070 H010100 N
070 H020100 N
070 I010100 N
070 I020100 N
070 J010100 Y
070 J020100 N
070 K010100 N
070 K020100 N
070 L010100 N
070 L020100 N
070 M010100 N
070 M020100 N
070 N010100 N
070 N020100 N
070 O010100 Y
070 O020100 N
070 P010100 Y
070 P020100 Y
070 Q010100 N
070 Q020100 N
070 R010100 N
070 R020100 N
071 A000100 538281
071 B000100 581065
071 C000100 592056
071 D000100 91
072 A000100 12
072 B000100 35748
<PAGE> PAGE 8
072 C000100 0
072 D000100 0
072 E000100 0
072 F000100 3302
072 G000100 116
072 H000100 0
072 I000100 197
072 J000100 61
072 K000100 0
072 L000100 40
072 M000100 39
072 N000100 65
072 O000100 0
072 P000100 0
072 Q000100 0
072 R000100 34
072 S000100 108
072 T000100 2037
072 U000100 0
072 V000100 0
072 W000100 22
072 X000100 6021
072 Y000100 0
072 Z000100 29727
072AA000100 18300
072BB000100 1270
072CC010100 110
072CC020100 0
072DD010100 12358
072DD020100 17370
072EE000100 0
073 A010100 0.0000
073 A020100 0.0000
073 B000100 0.0000
073 C000100 0.0000
074 A000100 29
074 B000100 0
074 C000100 11600
074 D000100 585969
074 E000100 0
074 F000100 0
074 G000100 0
074 H000100 0
074 I000100 0
074 J000100 16649
074 K000100 0
074 L000100 9811
074 M000100 86
074 N000100 624144
074 O000100 17109
074 P000100 416
<PAGE> PAGE 9
074 Q000100 0
074 R010100 0
074 R020100 0
074 R030100 0
074 R040100 1811
074 S000100 0
074 T000100 604808
074 U010100 20654
074 U020100 29100
074 V010100 0.00
074 V020100 0.00
074 W000100 0.0000
074 X000100 13545
074 Y000100 0
075 A000100 0
075 B000100 606768
076 000100 0.00
024 000200 N
028 A010200 956
028 A020200 138
028 A030200 0
028 A040200 848
028 B010200 2126
028 B020200 134
028 B030200 0
028 B040200 2615
028 C010200 821
028 C020200 170
028 C030200 0
028 C040200 1437
028 D010200 741
028 D020200 125
028 D030200 0
028 D040200 1249
028 E010200 780
028 E020200 157
028 E030200 0
028 E040200 2463
028 F010200 3648
028 F020200 122
028 F030200 0
028 F040200 1550
028 G010200 9072
028 G020200 846
028 G030200 0
028 G040200 10162
028 H000200 3042
029 000200 Y
030 A000200 10
030 B000200 4.00
030 C000200 0.00
<PAGE> PAGE 10
031 A000200 1
031 B000200 0
032 000200 0
033 000200 9
034 000200 Y
035 000200 102
036 A000200 N
036 B000200 0
037 000200 N
038 000200 0
039 000200 N
040 000200 Y
041 000200 Y
042 A000200 0
042 B000200 0
042 C000200 100
042 D000200 0
042 E000200 0
042 F000200 0
042 G000200 0
042 H000200 0
043 000200 373
044 000200 0
049 000200 N
050 000200 N
051 000200 N
052 000200 N
053 A000200 Y
053 B000200 Y
053 C000200 N
055 A000200 N
055 B000200 N
056 000200 Y
057 000200 N
058 A000200 N
059 000200 Y
060 A000200 N
060 B000200 N
061 000200 1000
062 A000200 Y
062 B000200 0.0
062 C000200 0.0
062 D000200 0.0
062 E000200 8.7
062 F000200 0.0
062 G000200 0.0
062 H000200 0.0
062 I000200 0.0
062 J000200 0.0
062 K000200 0.0
062 L000200 0.0
<PAGE> PAGE 11
062 M000200 0.0
062 N000200 0.0
062 O000200 92.7
062 P000200 0.0
062 Q000200 0.0
062 R000200 0.0
063 A000200 0
063 B000200 18.7
064 A000200 Y
064 B000200 N
070 A010200 Y
070 A020200 N
070 B010200 N
070 B020200 N
070 C010200 Y
070 C020200 N
070 D010200 N
070 D020200 N
070 E010200 Y
070 E020200 Y
070 F010200 N
070 F020200 N
070 G010200 Y
070 G020200 N
070 H010200 N
070 H020200 N
070 I010200 N
070 I020200 N
070 J010200 Y
070 J020200 N
070 K010200 Y
070 K020200 N
070 L010200 N
070 L020200 N
070 M010200 N
070 M020200 N
070 N010200 N
070 N020200 N
070 O010200 Y
070 O020200 N
070 P010200 Y
070 P020200 Y
070 Q010200 N
070 Q020200 N
070 R010200 N
070 R020200 N
071 A000200 72544
071 B000200 75751
071 C000200 87498
071 D000200 83
072 A000200 12
<PAGE> PAGE 12
072 B000200 5067
072 C000200 0
072 D000200 0
072 E000200 0
072 F000200 502
072 G000200 68
072 H000200 0
072 I000200 27
072 J000200 13
072 K000200 0
072 L000200 11
072 M000200 6
072 N000200 56
072 O000200 0
072 P000200 0
072 Q000200 0
072 R000200 27
072 S000200 28
072 T000200 373
072 U000200 6
072 V000200 0
072 W000200 5
072 X000200 1122
072 Y000200 6
072 Z000200 3951
072AA000200 2062
072BB000200 115
072CC010200 615
072CC020200 0
072DD010200 899
072DD020200 3052
072EE000200 0
073 A010200 0.0000
073 A020200 0.0000
073 B000200 0.0000
073 C000200 0.0000
074 A000200 62
074 B000200 0
074 C000200 8180
074 D000200 87092
074 E000200 0
074 F000200 0
074 G000200 0
074 H000200 0
074 I000200 0
074 J000200 0
074 K000200 0
074 L000200 1513
074 M000200 18
074 N000200 96865
074 O000200 2598
<PAGE> PAGE 13
074 P000200 68
074 Q000200 0
074 R010200 0
074 R020200 0
074 R030200 0
074 R040200 213
074 S000200 0
074 T000200 93986
074 U010200 2147
074 U020200 6765
074 V010200 0.00
074 V020200 0.00
074 W000200 0.0000
074 X000200 1710
074 Y000200 0
075 A000200 0
075 B000200 91577
076 000200 0.00
SIGNATURE GERALD M. RICHARD
TITLE TREASURER
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000765199
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL SERIES TRUST
<SERIES>
<NUMBER> 011
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL BOND FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> AUG-31-1998
<PERIOD-START> SEP-01-1997
<PERIOD-END> AUG-31-1998
<INVESTMENTS-AT-COST> 551425207
<INVESTMENTS-AT-VALUE> 597569168
<RECEIVABLES> 26459374
<ASSETS-OTHER> 115732
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 624144274
<PAYABLE-FOR-SECURITIES> 17109545
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 2226575
<TOTAL-LIABILITIES> 19336120
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 553547399
<SHARES-COMMON-STOCK> 3747608
<SHARES-COMMON-PRIOR> 3779839
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 5116794
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 46143961
<NET-ASSETS> 45544443
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 35748275
<OTHER-INCOME> 0
<EXPENSES-NET> (6020836)
<NET-INVESTMENT-INCOME> 29727439
<REALIZED-GAINS-CURRENT> 17029420
<APPREC-INCREASE-CURRENT> 110393
<NET-CHANGE-FROM-OPS> 46867252
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (2340837)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 506818
<NUMBER-OF-SHARES-REDEEMED> (626914)
<SHARES-REINVESTED> 87865
<NET-CHANGE-IN-ASSETS> (12066218)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (11912626)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 3301460
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 6020836
<AVERAGE-NET-ASSETS> 44688259
<PER-SHARE-NAV-BEGIN> 11.81
<PER-SHARE-NII> .63
<PER-SHARE-GAIN-APPREC> .34
<PER-SHARE-DIVIDEND> (.63)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 12.15
<EXPENSE-RATIO> .65
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000765199
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL SERIES TRUST
<SERIES>
<NUMBER> 012
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL BOND FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> AUG-31-1998
<PERIOD-START> SEP-01-1997
<PERIOD-END> AUG-31-1998
<INVESTMENTS-AT-COST> 551425207
<INVESTMENTS-AT-VALUE> 597569168
<RECEIVABLES> 26459374
<ASSETS-OTHER> 115732
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 624144274
<PAYABLE-FOR-SECURITIES> 17109545
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 2226575
<TOTAL-LIABILITIES> 19336120
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 553547399
<SHARES-COMMON-STOCK> 28059270
<SHARES-COMMON-PRIOR> 31819804
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 5116794
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 46143961
<NET-ASSETS> 341111427
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 35748275
<OTHER-INCOME> 0
<EXPENSES-NET> (6020836)
<NET-INVESTMENT-INCOME> 29727439
<REALIZED-GAINS-CURRENT> 17029420
<APPREC-INCREASE-CURRENT> 110393
<NET-CHANGE-FROM-OPS> 46867252
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (16812983)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 3238613
<NUMBER-OF-SHARES-REDEEMED> (7622437)
<SHARES-REINVESTED> 623290
<NET-CHANGE-IN-ASSETS> (12066218)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (11912626)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 3301460
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 6020836
<AVERAGE-NET-ASSETS> 355008531
<PER-SHARE-NAV-BEGIN> 11.82
<PER-SHARE-NII> .57
<PER-SHARE-GAIN-APPREC> .34
<PER-SHARE-DIVIDEND> (.57)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 12.16
<EXPENSE-RATIO> 1.16
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000765199
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL SERIES TRUST
<SERIES>
<NUMBER> 013
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL BOND FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> AUG-31-1998
<PERIOD-START> SEP-01-1997
<PERIOD-END> AUG-31-1998
<INVESTMENTS-AT-COST> 551425207
<INVESTMENTS-AT-VALUE> 597569168
<RECEIVABLES> 26459374
<ASSETS-OTHER> 115732
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 624144274
<PAYABLE-FOR-SECURITIES> 17109545
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 2226575
<TOTAL-LIABILITIES> 19336120
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 553547399
<SHARES-COMMON-STOCK> 1040386
<SHARES-COMMON-PRIOR> 922838
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 5116794
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 46143961
<NET-ASSETS> 12645617
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 35748275
<OTHER-INCOME> 0
<EXPENSES-NET> (6020836)
<NET-INVESTMENT-INCOME> 29727439
<REALIZED-GAINS-CURRENT> 17029420
<APPREC-INCREASE-CURRENT> 110393
<NET-CHANGE-FROM-OPS> 46867252
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (556750)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 500733
<NUMBER-OF-SHARES-REDEEMED> (411004)
<SHARES-REINVESTED> 27819
<NET-CHANGE-IN-ASSETS> (12066218)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (11912626)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 3301460
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 6020836
<AVERAGE-NET-ASSETS> 12032542
<PER-SHARE-NAV-BEGIN> 11.82
<PER-SHARE-NII> .55
<PER-SHARE-GAIN-APPREC> .33
<PER-SHARE-DIVIDEND> (.55)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 12.15
<EXPENSE-RATIO> 1.26
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000765199
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL SERIES TRUST
<SERIES>
<NUMBER> 014
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL BOND FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> AUG-31-1998
<PERIOD-START> SEP-01-1997
<PERIOD-END> AUG-31-1998
<INVESTMENTS-AT-COST> 551425207
<INVESTMENTS-AT-VALUE> 597569168
<RECEIVABLES> 26459374
<ASSETS-OTHER> 115732
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 624144274
<PAYABLE-FOR-SECURITIES> 17109545
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 2226575
<TOTAL-LIABILITIES> 19336120
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 553547399
<SHARES-COMMON-STOCK> 16906280
<SHARES-COMMON-PRIOR> 15682302
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 5116794
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 46143961
<NET-ASSETS> 205506667
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 35748275
<OTHER-INCOME> 0
<EXPENSES-NET> (6020836)
<NET-INVESTMENT-INCOME> 29727439
<REALIZED-GAINS-CURRENT> 17029420
<APPREC-INCREASE-CURRENT> 110393
<NET-CHANGE-FROM-OPS> 46867252
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (10016869)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 3096371
<NUMBER-OF-SHARES-REDEEMED> (2207281)
<SHARES-REINVESTED> 334888
<NET-CHANGE-IN-ASSETS> (12066218)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (11912626)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 3301460
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 6020836
<AVERAGE-NET-ASSETS> 195038257
<PER-SHARE-NAV-BEGIN> 11.82
<PER-SHARE-NII> .62
<PER-SHARE-GAIN-APPREC> .34
<PER-SHARE-DIVIDEND> (.62)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 12.16
<EXPENSE-RATIO> .75
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000765199
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL SERIES TRUST
<SERIES>
<NUMBER> 021
<NAME> MERRILL LYNCH CALIFORNIA INSURED MUNICIPAL BOND FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> AUG-31-1998
<PERIOD-START> SEP-01-1997
<PERIOD-END> AUG-31-1998
<INVESTMENTS-AT-COST> 89795561
<INVESTMENTS-AT-VALUE> 95271553
<RECEIVABLES> 1512782
<ASSETS-OTHER> 80767
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 96865102
<PAYABLE-FOR-SECURITIES> 2598189
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 281346
<TOTAL-LIABILITIES> 2879535
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 89375924
<SHARES-COMMON-STOCK> 1187422
<SHARES-COMMON-PRIOR> 1213650
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (866349)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 5475992
<NET-ASSETS> 12520426
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 5067158
<OTHER-INCOME> 0
<EXPENSES-NET> (1116102)
<NET-INVESTMENT-INCOME> 3951056
<REALIZED-GAINS-CURRENT> 1946789
<APPREC-INCREASE-CURRENT> 614862
<NET-CHANGE-FROM-OPS> 6512707
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (573903)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 138525
<NUMBER-OF-SHARES-REDEEMED> (187174)
<SHARES-REINVESTED> 22421
<NET-CHANGE-IN-ASSETS> 1927762
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (2813138)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 502296
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 1122459
<AVERAGE-NET-ASSETS> 12145607
<PER-SHARE-NAV-BEGIN> 10.25
<PER-SHARE-NII> .49
<PER-SHARE-GAIN-APPREC> .29
<PER-SHARE-DIVIDEND> (.49)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 10.54
<EXPENSE-RATIO> .82
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000765199
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL SERIES TRUST
<SERIES>
<NUMBER> 022
<NAME> MERRILL LYNCH CALIFORNIA INSURED MUNICIPAL BOND FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> AUG-31-1998
<PERIOD-START> SEP-01-1997
<PERIOD-END> AUG-31-1998
<INVESTMENTS-AT-COST> 89795561
<INVESTMENTS-AT-VALUE> 95271553
<RECEIVABLES> 1512782
<ASSETS-OTHER> 80767
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 96865102
<PAYABLE-FOR-SECURITIES> 2598189
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 281346
<TOTAL-LIABILITIES> 2879535
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 89375924
<SHARES-COMMON-STOCK> 6334960
<SHARES-COMMON-PRIOR> 6763433
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (866349)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 5475992
<NET-ASSETS> 66804025
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 5067158
<OTHER-INCOME> 0
<EXPENSES-NET> (1116102)
<NET-INVESTMENT-INCOME> 3951056
<REALIZED-GAINS-CURRENT> 1946789
<APPREC-INCREASE-CURRENT> 614862
<NET-CHANGE-FROM-OPS> 6512707
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (2846254)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 828509
<NUMBER-OF-SHARES-REDEEMED> (1368068)
<SHARES-REINVESTED> 111086
<NET-CHANGE-IN-ASSETS> 1927762
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (2813138)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 502296
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 1122459
<AVERAGE-NET-ASSETS> 67392026
<PER-SHARE-NAV-BEGIN> 10.25
<PER-SHARE-NII> .44
<PER-SHARE-GAIN-APPREC> .30
<PER-SHARE-DIVIDEND> (.44)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 10.55
<EXPENSE-RATIO> 1.32
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000765199
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL SERIES TRUST
<SERIES>
<NUMBER> 023
<NAME> MERRILL LYNCH CALIFORNIA INSURED MUNICIPAL BOND FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> AUG-31-1998
<PERIOD-START> SEP-01-1997
<PERIOD-END> AUG-31-1998
<INVESTMENTS-AT-COST> 89795561
<INVESTMENTS-AT-VALUE> 95271553
<RECEIVABLES> 1512782
<ASSETS-OTHER> 80767
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 96865102
<PAYABLE-FOR-SECURITIES> 2598189
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 281346
<TOTAL-LIABILITIES> 2879535
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 89375924
<SHARES-COMMON-STOCK> 430419
<SHARES-COMMON-PRIOR> 523342
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (866349)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 5475992
<NET-ASSETS> 4536704
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 5067158
<OTHER-INCOME> 0
<EXPENSES-NET> (1116102)
<NET-INVESTMENT-INCOME> 3951056
<REALIZED-GAINS-CURRENT> 1946789
<APPREC-INCREASE-CURRENT> 614862
<NET-CHANGE-FROM-OPS> 6512707
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (206008)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 179790
<NUMBER-OF-SHARES-REDEEMED> (282275)
<SHARES-REINVESTED> 9562
<NET-CHANGE-IN-ASSETS> 1927762
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (2813138)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 502296
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 1122459
<AVERAGE-NET-ASSETS> 4996458
<PER-SHARE-NAV-BEGIN> 10.24
<PER-SHARE-NII> .43
<PER-SHARE-GAIN-APPREC> .30
<PER-SHARE-DIVIDEND> (.43)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 10.54
<EXPENSE-RATIO> 1.42
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000765199
<NAME> MERRILL LYNCH CALIFORNIA MUNICIPAL SERIES TRUST
<SERIES>
<NUMBER> 024
<NAME> MERRILL LYNCH CALIFORNIA INSURED MUNICIPAL BOND FUND
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> AUG-31-1998
<PERIOD-START> SEP-01-1997
<PERIOD-END> AUG-31-1998
<INVESTMENTS-AT-COST> 89795561
<INVESTMENTS-AT-VALUE> 95271553
<RECEIVABLES> 1512782
<ASSETS-OTHER> 80767
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 96865102
<PAYABLE-FOR-SECURITIES> 2598189
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 281346
<TOTAL-LIABILITIES> 2879535
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 89375924
<SHARES-COMMON-STOCK> 959525
<SHARES-COMMON-PRIOR> 481550
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (866349)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 5475992
<NET-ASSETS> 10124412
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 5067158
<OTHER-INCOME> 0
<EXPENSES-NET> (1116102)
<NET-INVESTMENT-INCOME> 3951056
<REALIZED-GAINS-CURRENT> 1946789
<APPREC-INCREASE-CURRENT> 614862
<NET-CHANGE-FROM-OPS> 6512707
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (324891)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 527891
<NUMBER-OF-SHARES-REDEEMED> (69842)
<SHARES-REINVESTED> 19926
<NET-CHANGE-IN-ASSETS> 1927762
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> (2813138)
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 502296
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 1122459
<AVERAGE-NET-ASSETS> 7043276
<PER-SHARE-NAV-BEGIN> 10.26
<PER-SHARE-NII> .48
<PER-SHARE-GAIN-APPREC> .29
<PER-SHARE-DIVIDEND> (.48)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 10.55
<EXPENSE-RATIO> .92
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
