<PAGE> PAGE 1
000 B000000 12/31/1999
000 C000000 1059238
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 6.1
000 J000000 A
001 A000000 MERRIMAC SERIES
001 B000000 811-08741
001 C000000 8886377622
002 A000000 200 CLARENDON STREET
002 B000000 BOSTON
002 C000000 MA
002 D010000 02116
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 Y
007 B000000 5
007 C010100 1
007 C020100 MERRIMAC CASH SERIES
007 C030100 N
007 C010200 2
007 C020200 MERRIMAC TREASURY SERIES
007 C030200 N
007 C010300 3
007 C020300 MERRIMAC SHORT-TERM ASSET RESERVE SERIES
007 C030300 N
007 C010400 4
007 C020400 MERRIMAC TREASURY PLUS SERIES
007 C030400 N
007 C010500 5
007 C020500 MERRIMAC U.S. GOVERNMENT SERIES
007 C030500 N
007 C010600 6
007 C010700 7
007 C010800 8
007 C010900 9
007 C011000 10
010 A00AA01 INVESTORS BANK & TRUST COMPANY
010 C01AA01 BOSTON
010 C02AA01 MA
010 C03AA01 02116
011 A00AA01 FUNDS DISTRIBUTOR, INC.
011 B00AA01 8-20518
011 C01AA01 BOSTON
011 C02AA01 MA
011 C03AA01 02109
<PAGE> PAGE 2
012 A00AA01 INVESTORS BANK & TRUST COMPANY
012 B00AA01 85-720
012 C01AA01 BOSTON
012 C02AA01 MA
012 C03AA01 02116
013 A00AA01 ERNST & YOUNG L.L.P.
013 B01AA01 BOSTON
013 B02AA01 MA
013 B03AA01 02116
015 A00AA01 INVESTORS BANK & TRUST COMPANY
015 B00AA01 C
015 C01AA01 BOSTON
015 C02AA01 MA
015 C03AA01 02116
015 E01AA01 X
018 00AA00 Y
019 A00AA00 Y
019 B00AA00 11
019 C00AA00 MERRIMAC--
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 MERRIMAC CASH PORTFOLIO
022 B000001 04-3334601
022 C000001 1532406
022 D000001 1399474
022 A000002 MERRIMAC TREASURY PLUS PORTFOLIO
022 B000002 04-3449325
022 C000002 1227975
022 D000002 956287
022 A000003 MERRIMAC TREASURY PORTFOLIO
022 B000003 52-2021984
022 C000003 695213
022 D000003 638584
022 A000004 MERRIMAC U.S. GOVERNMENT PORTFOLIO
022 B000004 04-3466896
022 C000004 697418
022 D000004 569840
022 A000005 STANDISH STAR PORTFOLIO
022 B000005 04-3403866
022 C000005 34
022 D000005 1050
022 C000006 0
<PAGE> PAGE 3
022 D000006 0
022 C000007 0
022 D000007 0
022 C000008 0
022 D000008 0
022 C000009 0
022 D000009 0
022 C000010 0
022 D000010 0
023 C000000 4153046
023 D000000 3565235
024 00AA00 N
025 D00AA01 0
025 D00AA02 0
025 D00AA03 0
025 D00AA04 0
025 D00AA05 0
025 D00AA06 0
025 D00AA07 0
025 D00AA08 0
026 A000000 N
026 B000000 N
026 C000000 N
026 D000000 N
026 E000000 N
026 F000000 N
026 G010000 N
026 G020000 N
026 H000000 N
027 000000 Y
029 00AA00 N
030 A00AA00 0
030 B00AA00 0.00
030 C00AA00 0.00
031 A00AA00 0
031 B00AA00 0
032 00AA00 0
033 00AA00 0
034 00AA00 N
035 00AA00 0
036 B00AA00 0
037 00AA00 N
038 00AA00 0
039 00AA00 N
040 00AA00 Y
041 00AA00 N
042 A00AA00 0
042 B00AA00 0
042 C00AA00 0
042 D00AA00 0
042 E00AA00 0
<PAGE> PAGE 4
042 F00AA00 0
042 G00AA00 0
042 H00AA00 0
043 00AA00 0
044 00AA00 0
045 00AA00 N
048 00AA00 0.000
048 A01AA00 0
048 A02AA00 0.000
048 B01AA00 0
048 B02AA00 0.000
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 0
048 K02AA00 0.000
055 A00AA00 N
055 B00AA00 N
056 00AA00 N
057 00AA00 N
058 A00AA00 N
058 B00AA00 N
058 C00AA00 N
058 D00AA00 N
058 E00AA00 N
059 00AA00 Y
060 A00AA00 Y
060 B00AA00 Y
061 00AA00 10000
066 A00AA00 N
067 00AA00 N
068 A00AA00 N
068 B00AA00 N
069 00AA00 N
077 A000000 Y
077 B000000 Y
078 000000 N
080 A00AA00 NATIONAL UNION FIRE INSURANCE COMPANY
<PAGE> PAGE 5
080 C00AA00 2000
081 A00AA00 Y
081 B00AA00 6
082 A00AA00 Y
082 B00AA00 5
083 A00AA00 N
083 B00AA00 0
084 A00AA00 N
084 B00AA00 0
085 A00AA00 Y
085 B00AA00 N
028 A010100 277198
028 A020100 49
028 A030100 0
028 A040100 60531
028 B010100 103100
028 B020100 38
028 B030100 0
028 B040100 285613
028 C010100 62683
028 C020100 83
028 C030100 0
028 C040100 95196
028 D010100 192715
028 D020100 86
028 D030100 0
028 D040100 150739
028 E010100 116466
028 E020100 36
028 E030100 0
028 E040100 179137
028 F010100 109381
028 F020100 56
028 F030100 0
028 F040100 100525
028 G010100 861543
028 G020100 348
028 G030100 0
028 G040100 871741
028 H000100 0
062 A000100 Y
062 B000100 0.0
062 C000100 0.0
062 D000100 0.0
062 E000100 0.0
062 F000100 0.0
062 G000100 0.0
062 H000100 0.0
062 I000100 0.0
062 J000100 0.0
062 K000100 0.0
<PAGE> PAGE 6
062 L000100 100.5
062 M000100 0.0
062 N000100 0.0
062 O000100 0.0
062 P000100 0.0
062 Q000100 0.0
062 R000100 0.0
063 A000100 68
063 B000100 0.0
064 A000100 N
064 B000100 N
070 A010100 Y
070 A020100 N
070 B010100 N
070 B020100 N
070 C010100 N
070 C020100 N
070 D010100 N
070 D020100 N
070 E010100 N
070 E020100 N
070 F010100 N
070 F020100 N
070 G010100 N
070 G020100 N
070 H010100 N
070 H020100 N
070 I010100 N
070 I020100 N
070 J010100 Y
070 J020100 Y
070 K010100 Y
070 K020100 N
070 L010100 Y
070 L020100 Y
070 M010100 N
070 M020100 N
070 N010100 Y
070 N020100 N
070 O010100 Y
070 O020100 N
070 P010100 N
070 P020100 N
070 Q010100 N
070 Q020100 N
070 R010100 N
070 R020100 N
071 A000100 0
071 B000100 0
071 C000100 0
071 D000100 0
<PAGE> PAGE 7
072 A000100 12
072 B000100 13583
072 C000100 0
072 D000100 0
072 E000100 0
072 F000100 0
072 G000100 26
072 H000100 0
072 I000100 0
072 J000100 0
072 K000100 0
072 L000100 8
072 M000100 6
072 N000100 65
072 O000100 0
072 P000100 0
072 Q000100 0
072 R000100 13
072 S000100 5
072 T000100 0
072 U000100 3
072 V000100 0
072 W000100 615
072 X000100 741
072 Y000100 0
072 Z000100 12842
072AA000100 0
072BB000100 28
072CC010100 0
072CC020100 0
072DD010100 1118
072DD020100 11724
072EE000100 0
073 A010100 0.0510
073 A020100 0.0485
073 B000100 0.0000
073 C000100 0.0000
074 A000100 0
074 B000100 0
074 C000100 0
074 D000100 0
074 E000100 0
074 F000100 0
074 G000100 0
074 H000100 0
074 I000100 262416
074 J000100 0
074 K000100 0
074 L000100 0
074 M000100 16
074 N000100 262432
<PAGE> PAGE 8
074 O000100 0
074 P000100 0
074 Q000100 0
074 R010100 0
074 R020100 0
074 R030100 0
074 R040100 1403
074 S000100 0
074 T000100 261029
074 U010100 7231
074 U020100 253798
074 V010100 1.00
074 V020100 1.00
074 W000100 0.9995
074 X000100 12
074 Y000100 0
075 A000100 263028
075 B000100 0
076 000100 0.00
028 A010200 43855
028 A020200 0
028 A030200 0
028 A040200 78201
028 B010200 51494
028 B020200 0
028 B030200 0
028 B040200 31876
028 C010200 43555
028 C020200 0
028 C030200 0
028 C040200 30479
028 D010200 37368
028 D020200 0
028 D030200 0
028 D040200 49838
028 E010200 18102
028 E020200 0
028 E030200 0
028 E040200 45831
028 F010200 70056
028 F020200 0
028 F030200 0
028 F040200 61284
028 G010200 264430
028 G020200 0
028 G030200 0
028 G040200 297509
028 H000200 0
062 A000200 Y
062 B000200 0.0
062 C000200 0.0
<PAGE> PAGE 9
062 D000200 0.0
062 E000200 0.0
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 100.4
062 M000200 0.0
062 N000200 0.0
062 O000200 0.0
062 P000200 0.0
062 Q000200 0.0
062 R000200 0.0
063 A000200 24
063 B000200 0.0
064 A000200 N
064 B000200 N
070 A010200 N
070 A020200 N
070 B010200 N
070 B020200 N
070 C010200 N
070 C020200 N
070 D010200 N
070 D020200 N
070 E010200 N
070 E020200 N
070 F010200 N
070 F020200 N
070 G010200 N
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 Y
070 L010200 N
070 L020200 N
070 M010200 N
070 M020200 N
070 N010200 Y
070 N020200 N
070 O010200 Y
070 O020200 N
070 P010200 N
070 P020200 N
<PAGE> PAGE 10
070 Q010200 N
070 Q020200 N
070 R010200 N
070 R020200 N
071 A000200 0
071 B000200 0
071 C000200 0
071 D000200 0
072 A000200 12
072 B000200 7978
072 C000200 0
072 D000200 0
072 E000200 0
072 F000200 0
072 G000200 18
072 H000200 0
072 I000200 0
072 J000200 0
072 K000200 0
072 L000200 9
072 M000200 5
072 N000200 44
072 O000200 0
072 P000200 0
072 Q000200 0
072 R000200 12
072 S000200 6
072 T000200 0
072 U000200 2
072 V000200 0
072 W000200 396
072 X000200 492
072 Y000200 0
072 Z000200 7486
072AA000200 0
072BB000200 4
072CC010200 0
072CC020200 0
072DD010200 1163
072DD020200 6323
072EE000200 0
073 A010200 0.0386
073 A020200 0.0418
073 B000200 0.0000
073 C000200 0.0000
074 A000200 0
074 B000200 0
074 C000200 0
074 D000200 0
074 E000200 0
074 F000200 0
<PAGE> PAGE 11
074 G000200 0
074 H000200 0
074 I000200 179329
074 J000200 0
074 K000200 0
074 L000200 0
074 M000200 19
074 N000200 179348
074 O000200 0
074 P000200 0
074 Q000200 0
074 R010200 0
074 R020200 0
074 R030200 0
074 R040200 818
074 S000200 0
074 T000200 178530
074 U010200 24817
074 U020200 153715
074 V010200 1.00
074 V020200 1.00
074 W000200 1.0002
074 X000200 4
074 Y000200 0
075 A000200 177405
075 B000200 0
076 000200 0.00
028 A010300 0
028 A020300 0
028 A030300 0
028 A040300 0
028 B010300 0
028 B020300 0
028 B030300 0
028 B040300 0
028 C010300 0
028 C020300 0
028 C030300 0
028 C040300 0
028 D010300 0
028 D020300 0
028 D030300 0
028 D040300 0
028 E010300 0
028 E020300 0
028 E030300 0
028 E040300 0
028 F010300 0
028 F020300 0
028 F030300 0
028 F040300 0
<PAGE> PAGE 12
028 G010300 0
028 G020300 0
028 G030300 0
028 G040300 0
028 H000300 0
062 A000300 Y
062 B000300 0.0
062 C000300 0.0
062 D000300 0.0
062 E000300 0.0
062 F000300 0.0
062 G000300 0.0
062 H000300 0.0
062 I000300 0.0
062 J000300 0.0
062 K000300 0.0
062 L000300 0.0
062 M000300 0.0
062 N000300 0.0
062 O000300 0.0
062 P000300 0.0
062 Q000300 0.0
062 R000300 0.0
063 A000300 0
063 B000300 0.0
064 A000300 N
064 B000300 N
070 A010300 Y
070 A020300 N
070 B010300 Y
070 B020300 N
070 C010300 Y
070 C020300 N
070 D010300 Y
070 D020300 N
070 E010300 Y
070 E020300 N
070 F010300 Y
070 F020300 N
070 G010300 Y
070 G020300 N
070 H010300 Y
070 H020300 N
070 I010300 N
070 I020300 N
070 J010300 Y
070 J020300 N
070 K010300 Y
070 K020300 N
070 L010300 Y
070 L020300 N
<PAGE> PAGE 13
070 M010300 Y
070 M020300 N
070 N010300 Y
070 N020300 N
070 O010300 Y
070 O020300 N
070 P010300 N
070 P020300 N
070 Q010300 N
070 Q020300 N
070 R010300 N
070 R020300 N
071 A000300 0
071 B000300 0
071 C000300 0
071 D000300 0
072 A000300 12
072 B000300 23
072 C000300 0
072 D000300 0
072 E000300 0
072 F000300 0
072 G000300 0
072 H000300 0
072 I000300 0
072 J000300 0
072 K000300 0
072 L000300 0
072 M000300 0
072 N000300 8
072 O000300 0
072 P000300 0
072 Q000300 0
072 R000300 4
072 S000300 0
072 T000300 0
072 U000300 0
072 V000300 0
072 W000300 1
072 X000300 13
072 Y000300 13
072 Z000300 23
072AA000300 0
072BB000300 7
072CC010300 4
072CC020300 0
072DD010300 23
072DD020300 0
072EE000300 0
073 A010300 0.2204
073 A020300 0.0000
<PAGE> PAGE 14
073 B000300 0.0000
073 C000300 0.0000
074 A000300 0
074 B000300 0
074 C000300 0
074 D000300 0
074 E000300 0
074 F000300 0
074 G000300 0
074 H000300 0
074 I000300 0
074 J000300 0
074 K000300 4
074 L000300 0
074 M000300 0
074 N000300 4
074 O000300 0
074 P000300 0
074 Q000300 0
074 R010300 0
074 R020300 0
074 R030300 0
074 R040300 4
074 S000300 0
074 T000300 0
074 U010300 0
074 U020300 0
074 V010300 0.00
074 V020300 0.00
074 W000300 0.0000
074 X000300 0
074 Y000300 0
075 A000300 0
075 B000300 1031
076 000300 0.00
028 A010400 78908
028 A020400 0
028 A030400 0
028 A040400 87015
028 B010400 88630
028 B020400 0
028 B030400 0
028 B040400 47680
028 C010400 43032
028 C020400 0
028 C030400 0
028 C040400 66873
028 D010400 76344
028 D020400 0
028 D030400 0
028 D040400 48223
<PAGE> PAGE 15
028 E010400 116517
028 E020400 0
028 E030400 0
028 E040400 105525
028 F010400 204022
028 F020400 0
028 F030400 0
028 F040400 200563
028 G010400 607453
028 G020400 0
028 G030400 0
028 G040400 555879
028 H000400 0
062 A000400 Y
062 B000400 0.0
062 C000400 0.0
062 D000400 0.0
062 E000400 0.0
062 F000400 0.0
062 G000400 0.0
062 H000400 0.0
062 I000400 0.0
062 J000400 0.0
062 K000400 0.0
062 L000400 100.4
062 M000400 0.0
062 N000400 0.0
062 O000400 0.0
062 P000400 0.0
062 Q000400 0.0
062 R000400 0.0
063 A000400 8
063 B000400 0.0
064 A000400 N
064 B000400 N
070 A010400 Y
070 A020400 Y
070 B010400 N
070 B020400 N
070 C010400 N
070 C020400 N
070 D010400 N
070 D020400 N
070 E010400 N
070 E020400 N
070 F010400 N
070 F020400 N
070 G010400 N
070 G020400 N
070 H010400 N
070 H020400 N
<PAGE> PAGE 16
070 I010400 N
070 I020400 N
070 J010400 Y
070 J020400 N
070 K010400 Y
070 K020400 Y
070 L010400 N
070 L020400 N
070 M010400 N
070 M020400 N
070 N010400 Y
070 N020400 N
070 O010400 Y
070 O020400 N
070 P010400 N
070 P020400 N
070 Q010400 N
070 Q020400 N
070 R010400 N
070 R020400 N
071 A000400 0
071 B000400 0
071 C000400 0
071 D000400 0
072 A000400 12
072 B000400 11157
072 C000400 0
072 D000400 0
072 E000400 0
072 F000400 0
072 G000400 23
072 H000400 0
072 I000400 0
072 J000400 0
072 K000400 0
072 L000400 7
072 M000400 4
072 N000400 95
072 O000400 0
072 P000400 0
072 Q000400 0
072 R000400 10
072 S000400 5
072 T000400 0
072 U000400 0
072 V000400 0
072 W000400 597
072 X000400 741
072 Y000400 0
072 Z000400 10416
072AA000400 0
<PAGE> PAGE 17
072BB000400 0
072CC010400 0
072CC020400 0
072DD010400 10416
072DD020400 0
072EE000400 0
073 A010400 0.0420
073 A020400 0.0000
073 B000400 0.0000
073 C000400 0.0000
074 A000400 0
074 B000400 0
074 C000400 0
074 D000400 0
074 E000400 0
074 F000400 0
074 G000400 0
074 H000400 0
074 I000400 282844
074 J000400 0
074 K000400 0
074 L000400 0
074 M000400 13
074 N000400 282857
074 O000400 0
074 P000400 0
074 Q000400 0
074 R010400 0
074 R020400 0
074 R030400 0
074 R040400 1244
074 S000400 0
074 T000400 281613
074 U010400 281613
074 U020400 0
074 V010400 1.00
074 V020400 0.00
074 W000400 1.0001
074 X000400 2
074 Y000400 0
075 A000400 247663
075 B000400 0
076 000400 0.00
028 A010500 80862
028 A020500 0
028 A030500 0
028 A040500 95406
028 B010500 65473
028 B020500 0
028 B030500 0
028 B040500 72294
<PAGE> PAGE 18
028 C010500 83556
028 C020500 0
028 C030500 0
028 C040500 74483
028 D010500 101827
028 D020500 0
028 D030500 0
028 D040500 125686
028 E010500 52680
028 E020500 0
028 E030500 0
028 E040500 72136
028 F010500 143651
028 F020500 0
028 F030500 0
028 F040500 126728
028 G010500 528049
028 G020500 0
028 G030500 0
028 G040500 566733
028 H000500 0
062 A000500 Y
062 B000500 0.0
062 C000500 0.0
062 D000500 0.0
062 E000500 0.0
062 F000500 0.0
062 G000500 0.0
062 H000500 0.0
062 I000500 0.0
062 J000500 0.0
062 K000500 0.0
062 L000500 100.5
062 M000500 0.0
062 N000500 0.0
062 O000500 0.0
062 P000500 0.0
062 Q000500 0.0
062 R000500 0.0
063 A000500 66
063 B000500 0.0
064 A000500 N
064 B000500 N
070 A010500 Y
070 A020500 N
070 B010500 N
070 B020500 N
070 C010500 N
070 C020500 N
070 D010500 N
070 D020500 N
<PAGE> PAGE 19
070 E010500 N
070 E020500 N
070 F010500 N
070 F020500 N
070 G010500 N
070 G020500 N
070 H010500 N
070 H020500 N
070 I010500 N
070 I020500 N
070 J010500 Y
070 J020500 N
070 K010500 Y
070 K020500 Y
070 L010500 N
070 L020500 N
070 M010500 N
070 M020500 N
070 N010500 Y
070 N020500 N
070 O010500 Y
070 O020500 N
070 P010500 N
070 P020500 N
070 Q010500 N
070 Q020500 N
070 R010500 N
070 R020500 N
071 A000500 0
071 B000500 0
071 C000500 0
071 D000500 0
072 A000500 12
072 B000500 3739
072 C000500 0
072 D000500 0
072 E000500 0
072 F000500 0
072 G000500 6
072 H000500 0
072 I000500 0
072 J000500 0
072 K000500 0
072 L000500 1
072 M000500 1
072 N000500 55
072 O000500 0
072 P000500 0
072 Q000500 0
072 R000500 10
072 S000500 2
<PAGE> PAGE 20
072 T000500 0
072 U000500 0
072 V000500 0
072 W000500 185
072 X000500 260
072 Y000500 0
072 Z000500 3479
072AA000500 0
072BB000500 0
072CC010500 0
072CC020500 0
072DD010500 3479
072DD020500 0
072EE000500 0
073 A010500 0.0246
073 A020500 0.0000
073 B000500 0.0000
073 C000500 0.0000
074 A000500 0
074 B000500 0
074 C000500 0
074 D000500 0
074 E000500 0
074 F000500 0
074 G000500 0
074 H000500 0
074 I000500 131318
074 J000500 0
074 K000500 0
074 L000500 0
074 M000500 7
074 N000500 131325
074 O000500 0
074 P000500 0
074 Q000500 0
074 R010500 0
074 R020500 0
074 R030500 0
074 R040500 638
074 S000500 0
074 T000500 130687
074 U010500 130687
074 U020500 0
074 V010500 1.00
074 V020500 0.00
074 W000500 0.9996
074 X000500 1
074 Y000500 0
075 A000500 142096
075 B000500 0
076 000500 0.00
<PAGE> PAGE 21
SIGNATURE PAUL JASINSKI
TITLE TREASURER
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
This schedule contains summary financial information
extracted from Merrimac Series,
form N-SAR for the period ended December 31, 1999
and is qualified in its entirety by reference to
such financial statements.
</LEGEND>
<SERIES>
<NUMBER> 001
<NAME> Merrimac Cash Series Premium Class
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1999
<PERIOD-END> DEC-31-1999
<INVESTMENTS-AT-COST> 262,415,985
<INVESTMENTS-AT-VALUE> 262,415,985
<RECEIVABLES> 0
<ASSETS-OTHER> 7,116
<OTHER-ITEMS-ASSETS> 9,190
<TOTAL-ASSETS> 262,432,291
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 1,402,918
<TOTAL-LIABILITIES> 1,402,918
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 261,053,549
<SHARES-COMMON-STOCK> 7,235,148
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (3,643)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 7,231,505
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 1,171,813
<OTHER-INCOME> 0
<EXPENSES-NET> 53,323
<NET-INVESTMENT-INCOME> 1,118,490
<REALIZED-GAINS-CURRENT> (3,645)
<APPREC-INCREASE-CURRENT> 0
<NET-CHANGE-FROM-OPS> 1,114,845
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 1,118,490
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 265,910,695
<NUMBER-OF-SHARES-REDEEMED> 259,255,851
<SHARES-REINVESTED> 480,304
<NET-CHANGE-IN-ASSETS> 7,135,148
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 1,249,671
<AVERAGE-NET-ASSETS> 21,766,627
<PER-SHARE-NAV-BEGIN> 1.00
<PER-SHARE-NII> 0.05
<PER-SHARE-GAIN-APPREC> 0.00
<PER-SHARE-DIVIDEND> (0.05)
<PER-SHARE-DISTRIBUTIONS> 0.00
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 1.00
<EXPENSE-RATIO> 0.25
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
This schedule contains summary financial information
extracted from Merrimac Series,
form N-SAR for the period ended December 31, 1999
and is qualified in its entirety by reference to
such financial statements.
</LEGEND>
<SERIES>
<NUMBER> 002
<NAME> Merrimac Cash Series Institutional Class
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1999
<PERIOD-END> DEC-31-1999
<INVESTMENTS-AT-COST> 262,415,985
<INVESTMENTS-AT-VALUE> 262,415,985
<RECEIVABLES> 0
<ASSETS-OTHER> 7,116
<OTHER-ITEMS-ASSETS> 9,190
<TOTAL-ASSETS> 262,432,291
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 1,402,918
<TOTAL-LIABILITIES> 1,402,918
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 261,053,549
<SHARES-COMMON-STOCK> 253,818,401
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (20,534)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 253,797,867
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 12,919,883
<OTHER-INCOME> 0
<EXPENSES-NET> 1,196,348
<NET-INVESTMENT-INCOME> 11,723,535
<REALIZED-GAINS-CURRENT> (24,240)
<APPREC-INCREASE-CURRENT> 0
<NET-CHANGE-FROM-OPS> 11,699,295
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 11,723,535
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 1,265,945,943
<NUMBER-OF-SHARES-REDEEMED> 1,127,319,884
<SHARES-REINVESTED> 68,942
<NET-CHANGE-IN-ASSETS> 138,695,001
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 1,249,671
<AVERAGE-NET-ASSETS> 241,261,309
<PER-SHARE-NAV-BEGIN> 1.00
<PER-SHARE-NII> 0.05
<PER-SHARE-GAIN-APPREC> 0.00
<PER-SHARE-DIVIDEND> (0.05)
<PER-SHARE-DISTRIBUTIONS> 0.00
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 1.00
<EXPENSE-RATIO> 0.50
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
This schedule contains summary financial information
extracted from Merrimac Series,
form N-SAR for the period ended December 31, 1999
and is qualified in its entirety by reference to
such financial statements.
</LEGEND>
<SERIES>
<NUMBER> 004
<NAME> Merrimac Treasury Series Premium Class
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1999
<PERIOD-END> DEC-31-1999
<INVESTMENTS-AT-COST> 179,328,923
<INVESTMENTS-AT-VALUE> 179,328,923
<RECEIVABLES> 0
<ASSETS-OTHER> 11,413
<OTHER-ITEMS-ASSETS> 7,450
<TOTAL-ASSETS> 179,347,786
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 818,072
<TOTAL-LIABILITIES> 818,072
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 178,532,077
<SHARES-COMMON-STOCK> 24,816,639
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (579)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 24,816,060
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 1,235,791
<OTHER-INCOME> 0
<EXPENSES-NET> 72,714
<NET-INVESTMENT-INCOME> 1,163,077
<REALIZED-GAINS-CURRENT> (579)
<APPREC-INCREASE-CURRENT> 0
<NET-CHANGE-FROM-OPS> 1,162,498
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 1,163,077
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 120,340,322
<NUMBER-OF-SHARES-REDEEMED> 95,523,683
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> 24,816,639
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 873,526
<AVERAGE-NET-ASSETS> 30,285,792
<PER-SHARE-NAV-BEGIN> 1.00
<PER-SHARE-NII> 0.04
<PER-SHARE-GAIN-APPREC> 0.00
<PER-SHARE-DIVIDEND> (0.04)
<PER-SHARE-DISTRIBUTIONS> 0.00
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 1.00
<EXPENSE-RATIO> 0.28
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
This schedule contains summary financial information
extracted from Merrimac Series,
form N-SAR for the period ended December 31, 1999
and is qualified in its entirety by reference to
such financial statements.
</LEGEND>
<SERIES>
<NUMBER> 005
<NAME> Merrimac Treasury Series Institutional Cla
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1999
<PERIOD-END> DEC-31-1999
<INVESTMENTS-AT-COST> 179,328,923
<INVESTMENTS-AT-VALUE> 179,328,923
<RECEIVABLES> 0
<ASSETS-OTHER> 11,413
<OTHER-ITEMS-ASSETS> 7,450
<TOTAL-ASSETS> 179,347,786
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 818,072
<TOTAL-LIABILITIES> 818,072
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 178,532,077
<SHARES-COMMON-STOCK> 153,715,438
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (1,784)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 153,713,654
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 7,123,740
<OTHER-INCOME> 0
<EXPENSES-NET> 800,812
<NET-INVESTMENT-INCOME> 6,322,928
<REALIZED-GAINS-CURRENT> (3,053)
<APPREC-INCREASE-CURRENT> 0
<NET-CHANGE-FROM-OPS> 6,319,875
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 6,322,928
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 574,872,203
<NUMBER-OF-SHARES-REDEEMED> 535,476,952
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> 39,395,251
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 873,526
<AVERAGE-NET-ASSETS> 151,267,602
<PER-SHARE-NAV-BEGIN> 1.00
<PER-SHARE-NII> 0.04
<PER-SHARE-GAIN-APPREC> 0.00
<PER-SHARE-DIVIDEND> (0.04)
<PER-SHARE-DISTRIBUTIONS> 0.00
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 1.00
<EXPENSE-RATIO> 0.53
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
This schedule contains summary financial information
extracted from Merrimac Series,
form N-SAR for the period ended June 30, 1999
and is qualified in its entirety by reference to
such financial statements.
</LEGEND>
<SERIES>
<NUMBER> 7
<NAME> Merrimac STAR Series Premium Class
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1999
<PERIOD-END> DEC-31-1999
<INVESTMENTS-AT-COST> 0
<INVESTMENTS-AT-VALUE> 0
<RECEIVABLES> 3,575
<ASSETS-OTHER> 425
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 4,000
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 4,000
<TOTAL-LIABILITIES> 4,000
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 2,759
<SHARES-COMMON-STOCK> 0
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 132
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (2,891)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 0
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 24,438
<OTHER-INCOME> 0
<EXPENSES-NET> 1,486
<NET-INVESTMENT-INCOME> 22,952
<REALIZED-GAINS-CURRENT> (6,713)
<APPREC-INCREASE-CURRENT> 3,715
<NET-CHANGE-FROM-OPS> 19,954
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 22,820
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 0
<NUMBER-OF-SHARES-REDEEMED> 1,039,437
<SHARES-REINVESTED> 34,416
<NET-CHANGE-IN-ASSETS> (1,005,021)
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 14,123
<AVERAGE-NET-ASSETS> 1,031,389
<PER-SHARE-NAV-BEGIN> 9.97
<PER-SHARE-NII> 0.22
<PER-SHARE-GAIN-APPREC> (0.01)
<PER-SHARE-DIVIDEND> (0.22)
<PER-SHARE-DISTRIBUTIONS> 0.00
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 9.96
<EXPENSE-RATIO> 0.36
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
This schedule contains summary financial information
extracted from Merrimac Series,
form N-SAR for the period ended December 31, 1999
and is qualified in its entirety by reference to
such financial statements.
</LEGEND>
<SERIES>
<NUMBER> 011
<NAME> Merrimac Treasury Plus Series Institutiona
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1999
<PERIOD-END> DEC-31-1999
<INVESTMENTS-AT-COST> 282,844,598
<INVESTMENTS-AT-VALUE> 282,844,598
<RECEIVABLES> 0
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 12,768
<TOTAL-ASSETS> 282,857,366
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 1,244,663
<TOTAL-LIABILITIES> 1,244,663
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 281,612,769
<SHARES-COMMON-STOCK> 281,612,769
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (66)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 281,612,703
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 11,650,653
<OTHER-INCOME> 0
<EXPENSES-NET> 1,234,625
<NET-INVESTMENT-INCOME> 10,416,028
<REALIZED-GAINS-CURRENT> (66)
<APPREC-INCREASE-CURRENT> 0
<NET-CHANGE-FROM-OPS> 10,415,962
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 10,416,028
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 1,227,975,120
<NUMBER-OF-SHARES-REDEEMED> 946,362,351
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> 281,612,769
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 1,234,625
<AVERAGE-NET-ASSETS> 247,663,103
<PER-SHARE-NAV-BEGIN> 1.00
<PER-SHARE-NII> 0.04
<PER-SHARE-GAIN-APPREC> 0.00
<PER-SHARE-DIVIDEND> (0.04)
<PER-SHARE-DISTRIBUTIONS> 0.00
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 1.00
<EXPENSE-RATIO> 0.53
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
This schedule contains summary financial information
extracted from Merrimac Series,
form N-SAR for the period ended December 31, 1999
and is qualified in its entirety by reference to
such financial statements.
</LEGEND>
<SERIES>
<NUMBER> 015
<NAME> Merrimac U.S. Government Series Institutio
<S> <C>
<PERIOD-TYPE> 12-MOS
<FISCAL-YEAR-END> DEC-31-1999
<PERIOD-END> DEC-31-1999
<INVESTMENTS-AT-COST> 131,318,273
<INVESTMENTS-AT-VALUE> 131,318,273
<RECEIVABLES> 0
<ASSETS-OTHER> 7,004
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 131,325,277
<PAYABLE-FOR-SECURITIES> 0
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 638,542
<TOTAL-LIABILITIES> 638,542
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 130,685,729
<SHARES-COMMON-STOCK> 130,685,729
<SHARES-COMMON-PRIOR> 0
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 1,006
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 130,686,735
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 3,900,399
<OTHER-INCOME> 0
<EXPENSES-NET> 421,900
<NET-INVESTMENT-INCOME> 3,478,499
<REALIZED-GAINS-CURRENT> 1,006
<APPREC-INCREASE-CURRENT> 0
<NET-CHANGE-FROM-OPS> 3,479,505
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 3,478,499
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 697,418,162
<NUMBER-OF-SHARES-REDEEMED> 566,732,433
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> 130,685,729
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 0
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 421,900
<AVERAGE-NET-ASSETS> 142,095,964
<PER-SHARE-NAV-BEGIN> 1.00
<PER-SHARE-NII> 0.02
<PER-SHARE-GAIN-APPREC> 0.00
<PER-SHARE-DIVIDEND> (0.02)
<PER-SHARE-DISTRIBUTIONS> 0.00
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 1.00
<EXPENSE-RATIO> 0.58
</TABLE>
10
Report of Independent Auditors
To the Board of Trustees and
Shareholders of Merrimac Series
In planning and performing our audit of the financial statements of the Merrimac
Cash Series, the Merrimac Treasury Series, the Merrimac Treasury Plus Series,
the Merrimac U.S. Government Series, and the Merrimac STAR Series (collectively,
the "Series"), five of the series comprising the Merrimac Series (the "Trust"),
for the year ended December 31, 1999, we considered its internal control,
including control activities for safeguarding securities, in order to determine
our auditing procedures for the purpose of expressing our opinion on the
financial statements and to comply with the requirements of Form N-SAR, not to
provide assurance on internal control.
The management of the Trust is responsible for establishing and maintaining
internal control. In fulfilling this responsibility, estimates and judgments by
management are required to assess the expected benefits and related costs of
controls. Generally, controls that are relevant to an audit pertain to the
entity's objective of preparing financial statements for external purposes that
are fairly presented in conformity with generally accepted accounting
principles. Those controls include the safeguarding of assets against
unauthorized acquisition, use or disposition.
Because of inherent limitations in internal control, error or fraud may occur
and not be detected. Also, projection of any evaluation of internal control to
future periods is subject to the risk that it may become inadequate because of
changes in conditions or that the effectiveness of the design and operation may
deteriorate.
Our consideration of internal control would not necessarily disclose all matters
in internal control that might be material weaknesses under standards
established by the American Institute of Certified Public Accountants. A
material weakness is a condition in which the design or operation of one or more
of the internal control components does not reduce to a relatively low level the
risk that misstatements caused by error or fraud in amounts that would be
material in relation to the financial statements being audited may occur and not
be detected within a timely period by employees in the normal course of
performing their assigned functions. However, we noted no matters involving
internal control and its operation, including controls for safeguarding
securities, that we consider to be material weaknesses as defined above at
December 31, 1999.
This report is intended solely for the information and use of management, the
Board of Trustees of the Trust, and the Securities and Exchange Commission and
is not intended to be and should not be used by anyone other than these
specified parties.
February 11, 2000
