<PAGE> PAGE 1
000 B000000 12/31/98
000 C000000 0000067160
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 3.0.a
000 J000000 U
001 A000000 MML SERIES INVESTMENT FUND
001 B000000 811-2224
001 C000000 4137888411
002 A000000 1295 STATE STREET
002 B000000 SPRINGFIELD
002 C000000 MA
002 D010000 01111
002 D020000 0001
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 Y
007 B000000 6
007 C010100 1
007 C020100 MML EQUITY FUND
007 C030100 N
007 C010200 2
007 C020200 MML MONEY MARKET FUND
007 C030200 N
007 C010300 3
007 C020300 MML MANAGED BOND FUND
007 C030300 N
007 C010400 4
007 C020400 MML BLEND FUND
007 C030400 N
007 C010500 5
007 C020500 MML EQUITY INDEX FUND
007 C030500 N
007 C010600 6
007 C020600 MML SMALL CAP VALUE EQUITY FUND
007 C030600 N
007 C010700 7
007 C010800 8
007 C010900 9
007 C011000 10
014 A00AA01 MML INVESTORS SERVICES, INC.
014 B00AA01 8-27250
014 A00AA02 OPPENHEIMERFUNDS DISTRIBUTOR, INC.
014 B00AA02 8-22992
014 A00AA03 CENTENNIAL ASSET MANAGEMENT CORPORATION
014 B00AA03 8-22948
<PAGE> PAGE 2
014 A00AA04 MML DISTRIBUTORS, LLC
014 B00AA04 8-48203
014 A00AA05 BABSON SECURITIES CORPORATION
014 B00AA05 8-47589
014 A00AA06 JEFFERIES & COMPANY, INC.
014 B00AA06 8-00000
014 A00AA07 ADVEST, INC.
014 B00AA07 8-00000
020 A000001 BERNSTEIN (SANFORD C.) & CO.,INC
020 B000001 13-2625874
020 C000001 121
020 A000002 EXECUTION SERVICES
020 C000002 108
020 A000003 MORGAN STANLEY & CO. INCORPORATED
020 B000003 13-2655998
020 C000003 103
020 A000004 GOLDMAN SACHS & CO.
020 B000004 13-5108880
020 C000004 98
020 A000005 CREDIT SUISSE FIRST BOSTON CORPORATION
020 B000005 13-5659485
020 C000005 87
020 A000006 SCHRODER & CO.
020 B000006 13-2697472
020 C000006 81
020 A000007 DONALDSON, LUFKIN & JENRETTE SECURITIES CORP.
020 B000007 13-2741729
020 C000007 76
020 A000008 PAINEWEBBER INCORPORATED
020 B000008 13-2638166
020 C000008 71
020 A000009 BT ALEX. BROWN INCORPORATED
020 B000009 13-3311934
020 C000009 62
020 A000010 COWEN & CO
020 C000010 55
021 000000 1852
022 A000001 GOLDMAN SACHS & CO.
022 B000001 13-5108880
022 C000001 1305829
022 D000001 77663
022 A000002 MERRILL LYNCH, PIERCE, FENNER, & SMITH INC.
022 B000002 13-5674085
022 C000002 1326174
022 D000002 43760
022 A000003 MORGAN (J.P.) SECURITIES INC.
022 B000003 13-3224016
022 C000003 461550
022 D000003 48410
022 A000004 LEHMAN BROTHERS INC.
022 B000004 13-2518466
<PAGE> PAGE 3
022 C000004 399906
022 D000004 7392
022 A000005 CREDIT SUISSE FIRST BOSTON CORPORATION
022 B000005 13-5659485
022 C000005 477031
022 D000005 8465
022 A000006 BA SECURITIES, INC.
022 B000006 95-4035346
022 C000006 403449
022 D000006 0
022 A000007 MORGAN STANLEY & CO. INCORPORATED
022 B000007 13-2655998
022 C000007 135337
022 D000007 7392
022 A000008 SALOMON SMITH BARNEY
022 C000008 12182
022 D000008 6307
022 A000009 CHASE MANHATTAN BANK
022 C000009 44841
022 D000009 905
022 A000010 FIRST CHICAGO CAPITAL MARKETS, INC.
022 B000010 36-3595942
022 C000010 17687
022 D000010 0
023 C000000 8397311
023 D000000 638103
026 A000000 N
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
077 A000000 Y
077 B000000 Y
077 C000000 N
077 D000000 N
077 E000000 N
077 F000000 N
077 G000000 N
077 H000000 N
077 I000000 N
077 J000000 N
077 K000000 N
077 L000000 N
077 M000000 N
077 N000000 N
077 O000000 N
<PAGE> PAGE 4
077 P000000 N
077 Q010000 N
077 Q020000 N
077 Q030000 N
078 000000 N
080 A00AA00 NEW HAMPSHIRE INSURANCE COMPANY
080 C00AA00 5100
081 A00AA00 N
081 B00AA00 0
082 A00AA00 N
082 B00AA00 0
083 A00AA00 N
083 B00AA00 0
084 A00AA00 N
084 B00AA00 0
085 A00AA00 N
085 B00AA00 N
024 000100 N
025 D000101 0
025 D000102 0
025 D000103 0
025 D000104 0
025 D000105 0
025 D000106 0
025 D000107 0
025 D000108 0
028 A010100 32824
028 A020100 0
028 A030100 0
028 A040100 25008
028 B010100 16434
028 B020100 0
028 B030100 0
028 B040100 19628
028 C010100 15623
028 C020100 0
028 C030100 0
028 C040100 20531
028 D010100 15778
028 D020100 0
028 D030100 0
028 D040100 23674
028 E010100 17922
028 E020100 0
028 E030100 0
028 E040100 17182
028 F010100 19209
028 F020100 0
028 F030100 0
028 F040100 12033
028 G010100 117790
<PAGE> PAGE 5
028 G020100 0
028 G030100 0
028 G040100 118056
028 H000100 0
049 000100 N
050 000100 N
051 000100 N
052 000100 N
053 A000100 N
055 A000100 N
055 B000100 N
056 000100 Y
057 000100 N
058 A000100 N
059 000100 Y
060 A000100 Y
060 B000100 Y
061 000100 0
062 A000100 N
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
062 L000100 0.0
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 0
063 B000100 0.0
066 A000100 Y
066 B000100 N
066 C000100 N
066 D000100 N
066 E000100 Y
066 F000100 N
066 G000100 N
067 000100 N
068 A000100 N
068 B000100 N
069 000100 N
070 A010100 N
070 A020100 N
<PAGE> PAGE 6
070 B010100 Y
070 B020100 N
070 C010100 Y
070 C020100 N
070 D010100 Y
070 D020100 N
070 E010100 Y
070 E020100 N
070 F010100 Y
070 F020100 N
070 G010100 Y
070 G020100 N
070 H010100 Y
070 H020100 N
070 I010100 N
070 I020100 N
070 J010100 Y
070 J020100 N
070 K010100 Y
070 K020100 N
070 L010100 Y
070 L020100 N
070 M010100 N
070 M020100 N
070 N010100 N
070 N020100 N
070 O010100 Y
070 O020100 N
070 P010100 N
070 P020100 N
070 Q010100 Y
070 Q020100 N
070 R010100 N
070 R020100 N
071 A000100 532329
071 B000100 375620
071 C000100 2677092
071 D000100 14
072 A000100 12
072 B000100 6577
072 C000100 57979
072 D000100 0
072 E000100 0
072 F000100 10217
072 G000100 0
072 H000100 0
072 I000100 0
072 J000100 0
072 K000100 0
072 L000100 0
072 M000100 29
<PAGE> PAGE 7
072 N000100 0
072 O000100 0
072 P000100 0
072 Q000100 0
072 R000100 33
072 S000100 0
072 T000100 0
072 U000100 0
072 V000100 0
072 W000100 1
072 X000100 10280
072 Y000100 0
072 Z000100 54275
072AA000100 94862
072BB000100 0
072CC010100 271602
072CC020100 0
072DD010100 54285
072DD020100 0
072EE000100 94538
073 A010100 0.7240
073 A020100 0.0000
073 B000100 1.2610
073 C000100 0.0000
074 A000100 0
074 B000100 0
074 C000100 129097
074 D000100 0
074 E000100 0
074 F000100 2956278
074 G000100 0
074 H000100 0
074 I000100 0
074 J000100 16800
074 K000100 0
074 L000100 4606
074 M000100 0
074 N000100 3106781
074 O000100 16899
074 P000100 2571
074 Q000100 0
074 R010100 0
074 R020100 0
074 R030100 0
074 R040100 149204
074 S000100 0
074 T000100 2938107
074 U010100 74956
074 U020100 0
074 V010100 39.20
074 V020100 0.00
<PAGE> PAGE 8
074 W000100 0.0000
074 X000100 19
074 Y000100 0
075 A000100 0
075 B000100 2782765
076 000100 0.00
024 000200 N
025 A000201 DELETE
025 D000201 0
025 A000202 DELETE
025 D000202 0
025 A000203 DELETE
025 D000203 0
025 A000204 DELETE
025 D000204 0
025 D000205 0
025 D000206 0
025 D000207 0
025 D000208 0
028 A010200 9618
028 A020200 607
028 A030200 0
028 A040200 17207
028 B010200 23573
028 B020200 605
028 B030200 0
028 B040200 7986
028 C010200 27668
028 C020200 641
028 C030200 0
028 C040200 15823
028 D010200 24460
028 D020200 698
028 D030200 0
028 D040200 12481
028 E010200 7692
028 E020200 736
028 E030200 0
028 E040200 19372
028 F010200 22539
028 F020200 708
028 F030200 0
028 F040200 13597
028 G010200 115550
028 G020200 3995
028 G030200 0
028 G040200 86466
028 H000200 0
055 A000200 N
055 B000200 N
056 000200 Y
<PAGE> PAGE 9
057 000200 N
058 A000200 N
059 000200 Y
060 A000200 Y
060 B000200 Y
061 000200 0
062 A000200 Y
062 B000200 0.0
062 C000200 13.1
062 D000200 0.0
062 E000200 0.0
062 F000200 0.0
062 G000200 0.0
062 H000200 0.0
062 I000200 87.4
062 J000200 0.0
062 K000200 0.0
062 L000200 0.0
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 60
063 B000200 0.0
064 A000200 N
064 B000200 N
066 A000200 N
067 000200 N
068 A000200 N
068 B000200 N
069 000200 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 N
070 F010200 N
070 F020200 N
070 G010200 Y
070 G020200 N
070 H010200 N
070 H020200 N
070 I010200 N
070 I020200 N
<PAGE> PAGE 10
070 J010200 Y
070 J020200 N
070 K010200 Y
070 K020200 N
070 L010200 Y
070 L020200 N
070 M010200 N
070 M020200 N
070 N010200 N
070 N020200 N
070 O010200 Y
070 O020200 N
070 P010200 N
070 P020200 N
070 Q010200 Y
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 8413
072 C000200 0
072 D000200 0
072 E000200 0
072 F000200 694
072 G000200 0
072 H000200 0
072 I000200 0
072 J000200 0
072 K000200 0
072 L000200 0
072 M000200 27
072 N000200 0
072 O000200 0
072 P000200 0
072 Q000200 0
072 R000200 22
072 S000200 0
072 T000200 0
072 U000200 0
072 V000200 0
072 W000200 0
072 X000200 743
072 Y000200 0
072 Z000200 7670
072AA000200 0
072BB000200 1
072CC010200 0
<PAGE> PAGE 11
072CC020200 0
072DD010200 7669
072DD020200 0
072EE000200 0
073 A010200 0.5100
073 A020200 0.0000
073 B000200 0.0000
073 C000200 0.0000
074 A000200 10
074 B000200 0
074 C000200 179325
074 D000200 0
074 E000200 0
074 F000200 0
074 G000200 0
074 H000200 0
074 I000200 0
074 J000200 3395
074 K000200 0
074 L000200 711
074 M000200 0
074 N000200 183441
074 O000200 4077
074 P000200 181
074 Q000200 0
074 R010200 0
074 R020200 0
074 R030200 0
074 R040200 749
074 S000200 0
074 T000200 178434
074 U010200 178434
074 U020200 0
074 V010200 1.00
074 V020200 0.00
074 W000200 0.9994
074 X000200 18
074 Y000200 0
075 A000200 151986
075 B000200 0
076 000200 0.00
024 000300 Y
025 A000301 CHASE MANHATTAN BANK
025 C000301 D
025 D000301 3033
025 A000302 MERRILL LYNCH LTG INV
025 C000302 D
025 D000302 1696
025 A000303 CS FIRST BOSTON MORTGAGE
025 C000303 D
025 D000303 1006
<PAGE> PAGE 12
025 A000304 MORGAN STANLEY CAPITAL
025 C000304 D
025 D000304 414
025 D000305 0
025 D000306 0
025 D000307 0
025 D000308 0
028 A010300 2183
028 A020300 3358
028 A030300 0
028 A040300 1958
028 B010300 6170
028 B020300 0
028 B030300 0
028 B040300 691
028 C010300 6107
028 C020300 0
028 C030300 0
028 C040300 1073
028 D010300 10222
028 D020300 3657
028 D030300 0
028 D040300 1791
028 E010300 4524
028 E020300 0
028 E030300 0
028 E040300 2935
028 F010300 9117
028 F020300 0
028 F030300 0
028 F040300 4938
028 G010300 38323
028 G020300 7015
028 G030300 0
028 G040300 13386
028 H000300 0
055 A000300 Y
055 B000300 N
056 000300 Y
057 000300 N
058 A000300 N
059 000300 Y
060 A000300 Y
060 B000300 Y
061 000300 0
062 A000300 Y
062 B000300 0.0
062 C000300 0.0
062 D000300 0.0
062 E000300 0.0
062 F000300 0.0
<PAGE> PAGE 13
062 G000300 0.0
062 H000300 0.0
062 I000300 8.1
062 J000300 0.0
062 K000300 0.0
062 L000300 0.0
062 M000300 20.9
062 N000300 13.2
062 O000300 0.0
062 P000300 48.8
062 Q000300 10.2
062 R000300 0.0
063 A000300 0
063 B000300 10.9
064 A000300 Y
064 B000300 N
066 A000300 N
067 000300 N
068 A000300 N
068 B000300 N
069 000300 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 Y
070 K010300 Y
070 K020300 N
070 L010300 Y
070 L020300 Y
070 M010300 Y
070 M020300 N
070 N010300 Y
070 N020300 N
070 O010300 Y
070 O020300 N
<PAGE> PAGE 14
070 P010300 N
070 P020300 N
070 Q010300 Y
070 Q020300 N
070 R010300 N
070 R020300 N
071 A000300 127460
071 B000300 88975
071 C000300 213411
071 D000300 41
072 A000300 12
072 B000300 14982
072 C000300 0
072 D000300 0
072 E000300 0
072 F000300 1035
072 G000300 0
072 H000300 0
072 I000300 0
072 J000300 0
072 K000300 0
072 L000300 0
072 M000300 27
072 N000300 0
072 O000300 0
072 P000300 0
072 Q000300 0
072 R000300 29
072 S000300 0
072 T000300 0
072 U000300 0
072 V000300 0
072 W000300 2
072 X000300 1093
072 Y000300 0
072 Z000300 13889
072AA000300 1157
072BB000300 0
072CC010300 2666
072CC020300 0
072DD010300 13769
072DD020300 0
072EE000300 1157
073 A010300 0.7490
073 A020300 0.0000
073 B000300 0.0570
073 C000300 0.0000
074 A000300 2
074 B000300 0
074 C000300 20546
074 D000300 236700
<PAGE> PAGE 15
074 E000300 0
074 F000300 0
074 G000300 0
074 H000300 0
074 I000300 0
074 J000300 3471
074 K000300 0
074 L000300 2734
074 M000300 1
074 N000300 263454
074 O000300 4164
074 P000300 268
074 Q000300 0
074 R010300 0
074 R020300 0
074 R030300 0
074 R040300 4913
074 S000300 0
074 T000300 254109
074 U010300 20173
074 U020300 0
074 V010300 12.60
074 V020300 0.00
074 W000300 0.0000
074 X000300 18
074 Y000300 5237
075 A000300 0
075 B000300 228669
076 000300 0.00
024 000400 Y
025 A000401 CHASE MANHATTAN BANK
025 C000401 D
025 D000401 8309
025 A000402 MERRILL LYNCH MORTGAGE INC.
025 C000402 D
025 D000402 4360
025 A000403 CS FIRST BOSTON MORTGAGE
025 C000403 D
025 D000403 3019
025 A000404 MORGAN STANLEY CAPITAL
025 C000404 D
025 D000404 931
025 D000405 0
025 D000406 0
025 D000407 0
025 D000408 0
028 A010400 11038
028 A020400 24735
028 A030400 0
028 A040400 22389
028 B010400 11248
<PAGE> PAGE 16
028 B020400 0
028 B030400 0
028 B040400 16672
028 C010400 7752
028 C020400 0
028 C030400 0
028 C040400 17523
028 D010400 14046
028 D020400 0
028 D030400 0
028 D040400 17955
028 E010400 10830
028 E020400 24705
028 E030400 0
028 E040400 19037
028 F010400 11664
028 F020400 0
028 F030400 0
028 F040400 10372
028 G010400 66578
028 G020400 49440
028 G030400 0
028 G040400 103948
028 H000400 0
055 A000400 N
055 B000400 N
056 000400 Y
057 000400 N
058 A000400 N
059 000400 Y
060 A000400 Y
060 B000400 Y
061 000400 0
062 A000400 N
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 0.0
062 M000400 0.0
062 N000400 0.0
062 O000400 0.0
062 P000400 0.0
062 Q000400 0.0
062 R000400 0.0
<PAGE> PAGE 17
063 A000400 0
063 B000400 0.0
066 A000400 Y
066 B000400 N
066 C000400 N
066 D000400 N
066 E000400 N
066 F000400 N
066 G000400 Y
067 000400 N
068 A000400 N
068 B000400 N
069 000400 N
070 A010400 Y
070 A020400 N
070 B010400 Y
070 B020400 N
070 C010400 Y
070 C020400 N
070 D010400 Y
070 D020400 N
070 E010400 Y
070 E020400 N
070 F010400 Y
070 F020400 N
070 G010400 Y
070 G020400 N
070 H010400 Y
070 H020400 N
070 I010400 N
070 I020400 N
070 J010400 Y
070 J020400 Y
070 K010400 Y
070 K020400 N
070 L010400 Y
070 L020400 Y
070 M010400 Y
070 M020400 N
070 N010400 Y
070 N020400 N
070 O010400 Y
070 O020400 N
070 P010400 N
070 P020400 N
070 Q010400 Y
070 Q020400 N
070 R010400 N
070 R020400 N
071 A000400 704100
071 B000400 643991
<PAGE> PAGE 18
071 C000400 2223787
071 D000400 29
072 A000400 12
072 B000400 70820
072 C000400 35442
072 D000400 0
072 E000400 0
072 F000400 10258
072 G000400 0
072 H000400 0
072 I000400 0
072 J000400 0
072 K000400 0
072 L000400 0
072 M000400 27
072 N000400 0
072 O000400 0
072 P000400 0
072 Q000400 0
072 R000400 37
072 S000400 0
072 T000400 0
072 U000400 0
072 V000400 0
072 W000400 3
072 X000400 10325
072 Y000400 0
072 Z000400 95938
072AA000400 152811
072BB000400 0
072CC010400 109418
072CC020400 0
072DD010400 95855
072DD020400 0
072EE000400 152423
073 A010400 0.4160
073 A020400 0.0000
073 B000400 1.3580
073 C000400 0.0000
074 A000400 2
074 B000400 0
074 C000400 541828
074 D000400 676854
074 E000400 0
074 F000400 1771924
074 G000400 0
074 H000400 0
074 I000400 0
074 J000400 12061
074 K000400 0
074 L000400 12676
<PAGE> PAGE 19
074 M000400 1
074 N000400 3015346
074 O000400 21473
074 P000400 2583
074 Q000400 0
074 R010400 0
074 R020400 0
074 R030400 0
074 R040400 176601
074 S000400 0
074 T000400 2814689
074 U010400 112214
074 U020400 0
074 V010400 25.08
074 V020400 0.00
074 W000400 0.0000
074 X000400 15
074 Y000400 28176
075 A000400 0
075 B000400 2793914
076 000400 0.00
024 000500 Y
025 A000501 MORGAN STANLEY CAPITAL
025 C000501 E
025 D000501 151
025 A000502 CHASE MANHATTAN BANK
025 C000502 E
025 D000502 218
025 A000503 MERRILL LYNCH MORTGAGE
025 C000503 E
025 D000503 87
025 A000504 LEHMAN BROTHERS HOLDINGS INC.
025 B000504 13-3216325
025 C000504 E
025 D000504 18
025 A000505 BEAR STEARNS
025 C000505 E
025 D000505 15
025 D000506 0
025 D000507 0
025 D000508 0
055 A000500 N
055 B000500 N
056 000500 Y
057 000500 N
058 A000500 N
059 000500 Y
060 A000500 N
060 B000500 N
061 000500 0
062 A000500 N
<PAGE> PAGE 20
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 0.0
062 M000500 0.0
062 N000500 0.0
062 O000500 0.0
062 P000500 0.0
062 Q000500 0.0
062 R000500 0.0
066 A000500 Y
066 B000500 N
066 C000500 N
066 D000500 Y
066 E000500 N
066 F000500 N
066 G000500 N
067 000500 N
068 A000500 N
068 B000500 N
069 000500 Y
070 A010500 Y
070 A020500 N
070 B010500 Y
070 B020500 N
070 C010500 Y
070 C020500 N
070 D010500 Y
070 D020500 N
070 E010500 Y
070 E020500 N
070 F010500 Y
070 F020500 N
070 G010500 Y
070 G020500 N
070 H010500 Y
070 H020500 N
070 I010500 N
070 I020500 N
070 J010500 N
070 J020500 N
070 K010500 Y
070 K020500 N
070 L010500 Y
<PAGE> PAGE 21
070 L020500 Y
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 Y
070 Q020500 N
070 R010500 Y
070 R020500 N
071 A000500 5447
071 B000500 1523
071 C000500 29143
071 D000500 5
072 A000500 12
072 B000500 9
072 C000500 434
072 D000500 0
072 E000500 0
072 F000500 117
072 G000500 0
072 H000500 0
072 Y000500 30
072 Z000500 297
072AA000500 256
072BB000500 0
072CC010500 6832
072CC020500 0
072DD010500 297
072DD020500 0
072EE000500 239
073 A010500 0.1284
073 A020500 0.0000
073 B000500 0.1036
073 C000500 0.0000
074 A000500 0
074 B000500 615
074 C000500 0
074 D000500 0
074 E000500 0
074 F000500 35412
074 G000500 0
074 H000500 2
074 I000500 0
074 J000500 207
074 K000500 0
074 L000500 346
074 M000500 0
<PAGE> PAGE 22
074 N000500 36580
074 O000500 464
074 P000500 32
074 Q000500 0
074 R010500 0
074 R020500 0
074 R030500 0
074 R040500 15
074 S000500 0
074 T000500 36069
074 U010500 2364
074 U020500 0
074 V010500 15.26
074 V020500 0.00
074 W000500 0.0000
074 X000500 3
074 Y000500 0
075 A000500 0
075 B000500 29367
024 000600 N
028 A010600 0
028 A020600 0
028 A030600 0
028 A040600 0
028 B010600 1
028 B020600 0
028 B030600 0
028 B040600 0
028 C010600 110
028 C020600 0
028 C030600 0
028 C040600 0
028 D010600 463
028 D020600 0
028 D030600 0
028 D040600 2
028 E010600 628
028 E020600 0
028 E030600 0
028 E040600 20
028 F010600 700
028 F020600 0
028 F030600 0
028 F040600 42
028 G010600 1902
028 G020600 0
028 G030600 0
028 G040600 64
028 H000600 0
055 A000600 N
055 B000600 N
<PAGE> PAGE 23
056 000600 Y
057 000600 N
058 A000600 N
059 000600 Y
060 A000600 Y
060 B000600 Y
061 000600 0
062 A000600 N
062 B000600 0.0
062 C000600 0.0
062 D000600 0.0
062 E000600 0.0
062 F000600 0.0
062 G000600 0.0
062 H000600 0.0
062 I000600 0.0
062 J000600 0.0
062 K000600 0.0
062 L000600 0.0
062 M000600 0.0
062 N000600 0.0
062 O000600 0.0
062 P000600 0.0
062 Q000600 0.0
062 R000600 0.0
066 A000600 Y
066 B000600 N
066 C000600 N
066 D000600 N
066 E000600 Y
066 F000600 N
066 G000600 N
067 000600 N
068 A000600 N
068 B000600 N
069 000600 N
070 A010600 Y
070 A020600 N
070 B010600 Y
070 B020600 N
070 C010600 Y
070 C020600 N
070 D010600 Y
070 D020600 N
070 E010600 Y
070 E020600 N
070 F010600 Y
070 F020600 N
070 G010600 Y
070 G020600 N
070 H010600 Y
<PAGE> PAGE 24
070 H020600 N
070 I010600 N
070 I020600 N
070 J010600 Y
070 J020600 N
070 K010600 Y
070 K020600 N
070 L010600 Y
070 L020600 N
070 M010600 Y
070 M020600 N
070 N010600 Y
070 N020600 N
070 O010600 Y
070 O020600 N
070 P010600 N
070 P020600 N
070 Q010600 N
070 Q020600 N
070 R010600 Y
070 R020600 N
071 A000600 12395
071 B000600 1785
071 C000600 7631
071 D000600 23
072 A000600 7
072 B000600 30
072 C000600 46
072 D000600 0
072 E000600 0
072 F000600 35
072 G000600 0
072 H000600 0
072 I000600 0
072 J000600 0
072 K000600 0
072 L000600 0
072 M000600 14
072 N000600 0
072 O000600 0
072 P000600 0
072 Q000600 0
072 R000600 25
072 S000600 0
072 T000600 0
072 U000600 0
072 V000600 0
072 W000600 2
072 X000600 76
072 Y000600 36
072 Z000600 36
<PAGE> PAGE 25
072AA000600 0
072BB000600 276
072CC010600 0
072CC020600 1119
072DD010600 37
072DD020600 0
072EE000600 0
073 A010600 0.0300
073 A020600 0.0000
073 B000600 0.0000
073 C000600 0.0000
074 A000600 2244
074 B000600 0
074 C000600 0
074 D000600 0
074 E000600 0
074 F000600 9213
074 G000600 0
074 H000600 0
074 I000600 0
074 J000600 34
074 K000600 36
074 L000600 9
074 M000600 0
074 N000600 11536
074 O000600 1024
074 P000600 13
074 Q000600 0
074 R010600 0
074 R020600 0
074 R030600 0
074 R040600 57
074 S000600 0
074 T000600 10442
074 U010600 1229
074 U020600 0
074 V010600 8.49
074 V020600 0.00
074 W000600 0.0000
074 X000600 3
074 Y000600 0
075 A000600 0
075 B000600 9001
076 000600 0.00
SIGNATURE CHARLES C. MCCOBB, JR.
TITLE VICE PRESIDENT
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THE SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
REPORT TO SHAREHOLDERS OF MML SERIES INVESTMENT FUND FOR THE YEAR ENDED
DECEMBER 31, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000067160
<NAME> MML SERIES INVESTMENT FUND
<SERIES>
<NUMBER> 1
<NAME> MML EQUITY FUND
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-START> JAN-01-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 1,891,199,458
<INVESTMENTS-AT-VALUE> 3,085,375,157
<RECEIVABLES> 21,405,599
<ASSETS-OTHER> 511
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 3,106,781,267
<PAYABLE-FOR-SECURITIES> 16,898,542
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 151,775,261
<TOTAL-LIABILITIES> 168,673,803
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1,743,612,191
<SHARES-COMMON-STOCK> 74,956,036
<SHARES-COMMON-PRIOR> 66,682,603
<ACCUMULATED-NII-CURRENT> 7,107
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 312,467
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 1,194,175,699
<NET-ASSETS> 2,938,107,464
<DIVIDEND-INCOME> 57,978,788
<INTEREST-INCOME> 6,576,537
<OTHER-INCOME> 0
<EXPENSES-NET> 10,280,045
<NET-INVESTMENT-INCOME> 54,275,280
<REALIZED-GAINS-CURRENT> 94,862,149
<APPREC-INCREASE-CURRENT> 271,601,536
<NET-CHANGE-FROM-OPS> 420,738,965
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 54,285,000
<DISTRIBUTIONS-OF-GAINS> 94,537,870
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 7,903,059
<NUMBER-OF-SHARES-REDEEMED> 5,006,969
<SHARES-REINVESTED> 5,377,343
<NET-CHANGE-IN-ASSETS> 574,666,187
<ACCUMULATED-NII-PRIOR> 16,996
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 11,812
<GROSS-ADVISORY-FEES> 10,216,960
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 10,280,045
<AVERAGE-NET-ASSETS> 2,809,003,041
<PER-SHARE-NAV-BEGIN> 35.443
<PER-SHARE-NII> 0.724
<PER-SHARE-GAIN-APPREC> 5.016
<PER-SHARE-DIVIDEND> (0.724)
<PER-SHARE-DISTRIBUTIONS> (1.261)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 39.198
<EXPENSE-RATIO> 0.37
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THE SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
REPORT TO SHAREHOLDERS OF MML SERIES INVESTMENT FUND FOR THE YEAR ENDED
DECEMBER 31, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000067160
<NAME> MML SERIES INVESTMENT FUND
<SERIES>
<NUMBER> 2
<NAME> MML MONEY MARKET FUND
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-START> JAN-01-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 179,325,017
<INVESTMENTS-AT-VALUE> 179,325,017
<RECEIVABLES> 4,105,599
<ASSETS-OTHER> 10,387
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 183,441,003
<PAYABLE-FOR-SECURITIES> 4,077,493
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 929,753
<TOTAL-LIABILITIES> 5,007,246
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 178,433,757
<SHARES-COMMON-STOCK> 178,433,757
<SHARES-COMMON-PRIOR> 141,165,385
<ACCUMULATED-NII-CURRENT> 14,087
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> (11,997)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 0
<NET-ASSETS> 178,433,757
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 8,412,554
<OTHER-INCOME> 0
<EXPENSES-NET> 743,005
<NET-INVESTMENT-INCOME> 7,669,549
<REALIZED-GAINS-CURRENT> (96)
<APPREC-INCREASE-CURRENT> 0
<NET-CHANGE-FROM-OPS> 7,669,453
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (7,669,453)
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 188,771,360
<NUMBER-OF-SHARES-REDEEMED> 159,080,164
<SHARES-REINVESTED> 7,577,176
<NET-CHANGE-IN-ASSETS> 37,268,372
<ACCUMULATED-NII-PRIOR> 13,560
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> (13,560)
<GROSS-ADVISORY-FEES> 693,453
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 743,005
<AVERAGE-NET-ASSETS> 151,985,816
<PER-SHARE-NAV-BEGIN> 1.00
<PER-SHARE-NII> 0.50
<PER-SHARE-GAIN-APPREC> 0
<PER-SHARE-DIVIDEND> (0.50)
<PER-SHARE-DISTRIBUTIONS> (0.50)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 1.00
<EXPENSE-RATIO> 0.491
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THE SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
REPORT TO SHAREHOLDERS OF MML SERIES INVESTMENT FUND FOR THE YEAR ENDED
DECEMBER 31, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000067160
<NAME> MML SERIES INVESTMENT FUND
<SERIES>
<NUMBER> 3
<NAME> MML MANAGED BOND FUND
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-START> JAN-01-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 248,132,243
<INVESTMENTS-AT-VALUE> 257,245,988
<RECEIVABLES> 6,205,244
<ASSETS-OTHER> 2,582
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 263,453,814
<PAYABLE-FOR-SECURITIES> 4,164,455
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 5,180,679
<TOTAL-LIABILITIES> 9,345,134
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 244,874,906
<SHARES-COMMON-STOCK> 20,173,153
<SHARES-COMMON-PRIOR> 16,545,756
<ACCUMULATED-NII-CURRENT> 120,030
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 0
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 9,113,744
<NET-ASSETS> 254,108,680
<DIVIDEND-INCOME> 0
<INTEREST-INCOME> 14,982,005
<OTHER-INCOME> 0
<EXPENSES-NET> 1,092,750
<NET-INVESTMENT-INCOME> 13,889,255
<REALIZED-GAINS-CURRENT> 1,157,167
<APPREC-INCREASE-CURRENT> 2,666,019
<NET-CHANGE-FROM-OPS> 17,712,441
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (13,769,225)
<DISTRIBUTIONS-OF-GAINS> (1,157,166)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 4,363,667
<NUMBER-OF-SHARES-REDEEMED> 1,816,564
<SHARES-REINVESTED> 1,080,294
<NET-CHANGE-IN-ASSETS> 48,792,782
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 705
<OVERDISTRIB-NII-PRIOR> 96,215
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 1,034,821
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 1,092,750
<AVERAGE-NET-ASSETS> 228,857,737
<PER-SHARE-NAV-BEGIN> 12.41
<PER-SHARE-NII> 0.756
<PER-SHARE-GAIN-APPREC> 0.236
<PER-SHARE-DIVIDEND> (0.749)
<PER-SHARE-DISTRIBUTIONS> (0.57)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 12.59
<EXPENSE-RATIO> 0.48
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THE SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
REPORT TO SHAREHOLDERS OF MML SERIES INVESTMENT FUND FOR THE YEAR ENDED
DECEMBER 31, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000067160
<NAME> MML SERIES INVESTMENT FUND
<SERIES>
<NUMBER> 4
<NAME> MML BLEND FUND
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-START> JAN-01-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 2,140,545,032
<INVESTMENTS-AT-VALUE> 2,990,606,154
<RECEIVABLES> 24,737,439
<ASSETS-OTHER> 2,606
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 3,015,346,199
<PAYABLE-FOR-SECURITIES> 21,472,744
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 179,184,545
<TOTAL-LIABILITIES> 200,657,289
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 1,964,351,614
<SHARES-COMMON-STOCK> 112,214,264
<SHARES-COMMON-PRIOR> 102,652,434
<ACCUMULATED-NII-CURRENT> 82,185
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 193,989
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 850,061,122
<NET-ASSETS> 2,814,688,910
<DIVIDEND-INCOME> 35,442,402
<INTEREST-INCOME> 70,820,208
<OTHER-INCOME> 0
<EXPENSES-NET> 10,325,081
<NET-INVESTMENT-INCOME> 95,937,529
<REALIZED-GAINS-CURRENT> 152,811,311
<APPREC-INCREASE-CURRENT> 109,417,834
<NET-CHANGE-FROM-OPS> 358,166,674
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (95,855,344)
<DISTRIBUTIONS-OF-GAINS> (152,423,440)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 6,180,424
<NUMBER-OF-SHARES-REDEEMED> 7,166,826
<SHARES-REINVESTED> 10,548,232
<NET-CHANGE-IN-ASSETS> 342,861,419
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 53,700
<OVERDIST-NET-GAINS-PRIOR> 140,182
<GROSS-ADVISORY-FEES> 10,258,331
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 10,325,081
<AVERAGE-NET-ASSETS> 2,814,104,104
<PER-SHARE-NAV-BEGIN> 24.08
<PER-SHARE-NII> 0.417
<PER-SHARE-GAIN-APPREC> 2.36
<PER-SHARE-DIVIDEND> (0.416)
<PER-SHARE-DISTRIBUTIONS> (1.358)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 25.083
<EXPENSE-RATIO> 0.371
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THE SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
REPORT TO SHAREHOLDERS OF MML SERIES INVESTMENT FUND FOR THE YEAR ENDED
DECEMBER 31, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000067160
<NAME> MML SERIES INVESTMENT FUND
<SERIES>
<NUMBER> 5
<NAME> MML EQUITY INDEX FUND
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-START> JAN-01-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 25,048,465
<INVESTMENTS-AT-VALUE> 36,027,451
<RECEIVABLES> 550,481
<ASSETS-OTHER> 0
<OTHER-ITEMS-ASSETS> 1,871
<TOTAL-ASSETS> 36,579,803
<PAYABLE-FOR-SECURITIES> 463,926
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 46,600
<TOTAL-LIABILITIES> 510,526
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 25,042,705
<SHARES-COMMON-STOCK> 2,363,757
<SHARES-COMMON-PRIOR> 2,002,675
<ACCUMULATED-NII-CURRENT> 682
<OVERDISTRIBUTION-NII> 0
<ACCUMULATED-NET-GAINS> 22,670
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 11,003,220
<NET-ASSETS> 36,069,277
<DIVIDEND-INCOME> 433,812
<INTEREST-INCOME> 9,179
<OTHER-INCOME> 0
<EXPENSES-NET> 145,796
<NET-INVESTMENT-INCOME> 297,195
<REALIZED-GAINS-CURRENT> 255,853
<APPREC-INCREASE-CURRENT> 6,831,658
<NET-CHANGE-FROM-OPS> 7,384,706
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> (296,748)
<DISTRIBUTIONS-OF-GAINS> (239,134)
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 333,870
<NUMBER-OF-SHARES-REDEEMED> (7,976)
<SHARES-REINVESTED> 35,188
<NET-CHANGE-IN-ASSETS> 11,867,514
<ACCUMULATED-NII-PRIOR> 235
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> (54)
<GROSS-ADVISORY-FEES> 117,349
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 175,494
<AVERAGE-NET-ASSETS> 29,367,453
<PER-SHARE-NAV-BEGIN> 12.08
<PER-SHARE-NII> 0.13
<PER-SHARE-GAIN-APPREC> 3.28
<PER-SHARE-DIVIDEND> (0.13)
<PER-SHARE-DISTRIBUTIONS> (0.10)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 15.26
<EXPENSE-RATIO> 0.50
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<LEGEND>
THE SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATIOM EXTRACTED FROM THE
REPORT TO SHAREHOLDERS OF MML SERIES INVESTMENT FUND FOR THE YEAR ENDED
DECEMBER 31, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000067160
<NAME> MML SERIES INVESTMENT FUND
<SERIES>
<NUMBER> 6
<NAME> MML SMALL CAP VALUE EQUITY FUND
<S> <C>
<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> DEC-31-1998
<PERIOD-START> JUN-01-1998
<PERIOD-END> DEC-31-1998
<INVESTMENTS-AT-COST> 10,332,136
<INVESTMENTS-AT-VALUE> 9,212,701
<RECEIVABLES> 79,284
<ASSETS-OTHER> 2,244,086
<OTHER-ITEMS-ASSETS> 0
<TOTAL-ASSETS> 11,536,071
<PAYABLE-FOR-SECURITIES> 1,023,600
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 70,287
<TOTAL-LIABILITIES> 1,093,887
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 11,838,877
<SHARES-COMMON-STOCK> 1,229,502
<SHARES-COMMON-PRIOR> 1,000,000
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> 914
<ACCUMULATED-NET-GAINS> (276,344)
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> (1,119,435)
<NET-ASSETS> 10,442,184
<DIVIDEND-INCOME> 46,135
<INTEREST-INCOME> 30,115
<OTHER-INCOME> 0
<EXPENSES-NET> 39,727
<NET-INVESTMENT-INCOME> 36,523
<REALIZED-GAINS-CURRENT> (276,344)
<APPREC-INCREASE-CURRENT> (1,119,435)
<NET-CHANGE-FROM-OPS> (1,359,256)
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 37,437
<DISTRIBUTIONS-OF-GAINS> 0
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 1,237,251
<NUMBER-OF-SHARES-REDEEMED> (7,749)
<SHARES-REINVESTED> 0
<NET-CHANGE-IN-ASSETS> 10,442,184
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 0
<OVERDISTRIB-NII-PRIOR> 0
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 35,260
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 76,161
<AVERAGE-NET-ASSETS> 8,964,387
<PER-SHARE-NAV-BEGIN> 10
<PER-SHARE-NII> 0.03
<PER-SHARE-GAIN-APPREC> (1.51)
<PER-SHARE-DIVIDEND> (0.03)
<PER-SHARE-DISTRIBUTIONS> 0
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 8.49
<EXPENSE-RATIO> 0.44
<AVG-DEBT-OUTSTANDING> 0
<AVG-DEBT-PER-SHARE> 0
</TABLE>
EXHIBIT INDEX TO FORM N-SAR
OF MML SERIES INVESTMENT FUND
FOR THE PERIOD ENDED DECEMBER 31, 1998
Exhibit No. Description
77B Accountant's report on internal control
PRICEWATERHOUSECOOOPERS LLP
PricewaterhouseCoopers LLP
2300 BayBank Tower
P.O. Box 59
Springfield MA 01101-0059
Telephone (413) 781 7200
Facsimile (413) 733 2195
Report of Independent Accountants
To the Board of Trustees and Shareholders of
MML Series Investment Fund
In planning and performing our audit of the financial statements and
financial highlights of each of the funds which comprise the MML Series
Investment Fund (hereafter referred to as the "Fund") for the year ended
December 31, 1998, we considered its internal control, including control
activities over safeguarding securities, in order to determine our auditing
procedures for the purpose of expressing our opinion on the financial
statements and financial highlights and to comply with the requirements of
Form N-SAR, not to provide assurance on internal control.
The management of the Fund 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 error or fraud in amounts that would be material in
relation to the financial statements and financial highlights 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 as of December 31, 1998.
This report is intended solely for the information and use of the Board of
Trustees and management of the Fund and the Securities and Exchange
Commission.
PricewaterhouseCoopers LLP
Springfield, Massachusetts
February 25, 1999
