<PAGE> PAGE 1
000 A000000 06/30/2000
000 C000000 933188
000 D000000 N
000 E000000 NF
000 F000000 Y
000 G000000 N
000 H000000 N
000 I000000 6.1
000 J000000 A
001 A000000 SENIOR DEBT PORTFOLIO
001 B000000 811-8876
001 C000000 6174828260
002 A000000 255 STATE STREET
002 B000000 BOSTON
002 C000000 MA
002 D010000 02109
003 000000 N
004 000000 N
005 000000 N
006 000000 N
007 A000000 N
007 B000000 0
007 C010100 1
007 C010200 2
007 C010300 3
007 C010400 4
007 C010500 5
007 C010600 6
007 C010700 7
007 C010800 8
007 C010900 9
007 C011000 10
008 A000001 BOSTON MANAGEMENT AND RESEARCH
008 B000001 A
008 C000001 801-15930
008 D010001 BOSTON
008 D020001 MA
008 D030001 02109
011 A000001 DELETE
012 A000001 DELETE
013 A000001 DELOITTE & TOUCHE LLP
013 B010001 BOSTON
013 B020001 MA
013 B030001 02116
014 A000001 EATON VANCE DISTRIBUTORS, INC.
014 B000001 8-24081
015 A000001 INVESTORS BANK & TRUST COMPANY
015 B000001 C
015 C010001 BOSTON
015 C020001 MA
015 C030001 02116
<PAGE> PAGE 2
015 E010001 X
018 000000 Y
019 A000000 Y
019 B000000 163
019 C000000 EATONVANCE
020 A000001 BEAR STEARNS
020 C000001 419
020 A000002 CITIBANK
020 C000002 50
020 A000003 GOLDMAN SACHS
020 C000003 40
020 A000004 LEHMAN BROTHERS
020 C000004 25
020 A000005 DLJ
020 C000005 11
020 A000006 IMPERIAL SAVINGS
020 C000006 10
020 A000007 CHASE MANHATTAN
020 C000007 8
020 A000008 INVESCO
020 C000008 4
020 A000009 FIRST UNION
020 C000009 3
020 A000010 BANKERS TRUST
020 C000010 2
021 000000 577
022 A000001 THE COMPANY
022 C000001 43246934
022 D000001 0
022 A000002 CONVERSION
022 C000002 2198390
022 D000002 5463340
022 A000003 SMITH BARNEY
022 C000003 2143728
022 D000003 0
022 A000004 MBS PRINCIPAL PAYDOWN
022 C000004 37106
022 D000004 1355975
022 A000005 BANKERS TRUST
022 C000005 1292294
022 D000005 0
022 A000006 INTERNAL SWAP
022 C000006 384689
022 D000006 364823
022 A000007 MERRILL LYNCH
022 C000007 721291
022 D000007 2000
022 A000008 GOLDMAN
022 C000008 712533
022 D000008 5000
022 A000009 CREDIT SUISSE
<PAGE> PAGE 3
022 C000009 641580
022 D000009 0
022 A000010 CHASE MANHATTAN
022 C000010 458440
022 D000010 110441
023 C000000 53800163
023 D000000 7573675
024 000000 N
026 A000000 N
026 B000000 N
026 C000000 N
026 D000000 Y
026 E000000 N
026 F000000 N
026 G010000 N
026 G020000 N
026 H000000 N
027 000000 N
045 000000 Y
046 000000 N
047 000000 Y
048 000000 0.000
048 A010000 1000000
048 A020000 0.500
048 B010000 1000000
048 B020000 0.450
048 C010000 5000000
048 C020000 0.400
048 D010000 3000000
048 D020000 0.388
048 E010000 0
048 E020000 0.375
048 F010000 0
048 F020000 0.000
048 G010000 0
048 G020000 0.000
048 H010000 0
048 H020000 0.000
048 I010000 0
048 I020000 0.000
048 J010000 0
048 J020000 0.000
048 K010000 0
048 K020000 0.000
049 000000 N
050 000000 N
051 000000 N
052 000000 N
053 A000000 N
054 A000000 Y
054 B000000 Y
<PAGE> PAGE 4
054 C000000 N
054 D000000 N
054 E000000 N
054 F000000 N
054 G000000 Y
054 H000000 Y
054 I000000 N
054 J000000 Y
054 K000000 N
054 L000000 N
054 M000000 Y
054 N000000 N
054 O000000 N
055 A000000 N
055 B000000 N
056 000000 Y
057 000000 N
058 A000000 N
059 000000 Y
060 A000000 N
060 B000000 N
061 000000 0
062 A000000 N
062 B000000 0.0
062 C000000 0.0
062 D000000 0.0
062 E000000 0.0
062 F000000 0.0
062 G000000 0.0
062 H000000 0.0
062 I000000 0.0
062 J000000 0.0
062 K000000 0.0
062 L000000 0.0
062 M000000 0.0
062 N000000 0.0
062 O000000 0.0
062 P000000 0.0
062 Q000000 0.0
062 R000000 0.0
066 A000000 N
067 000000 N
068 A000000 N
068 B000000 N
069 000000 N
070 A010000 Y
070 A020000 N
070 B010000 Y
070 B020000 N
070 C010000 Y
070 C020000 N
<PAGE> PAGE 5
070 D010000 Y
070 D020000 N
070 E010000 Y
070 E020000 N
070 F010000 Y
070 F020000 N
070 G010000 Y
070 G020000 N
070 H010000 Y
070 H020000 N
070 I010000 N
070 I020000 N
070 J010000 Y
070 J020000 Y
070 K010000 Y
070 K020000 N
070 L010000 Y
070 L020000 N
070 M010000 Y
070 M020000 N
070 N010000 Y
070 N020000 N
070 O010000 Y
070 O020000 Y
070 P010000 N
070 P020000 N
070 Q010000 N
070 Q020000 N
070 R010000 Y
070 R020000 N
071 A000000 2579811
071 B000000 2361167
071 C000000 8180202
071 D000000 29
072 A000000 6
072 B000000 411152
072 C000000 0
072 D000000 0
072 E000000 4894
072 F000000 19583
072 G000000 0
072 H000000 0
072 I000000 0
072 J000000 739
072 K000000 0
072 L000000 0
072 M000000 1
072 N000000 0
072 O000000 0
072 P000000 274
072 Q000000 0
<PAGE> PAGE 6
072 R000000 95
072 S000000 298
072 T000000 0
072 U000000 3
072 V000000 0
072 W000000 130
072 X000000 21123
072 Y000000 0
072 Z000000 394923
072AA000000 0
072BB000000 14069
072CC010000 0
072CC020000 40556
072DD010000 0
072DD020000 0
072EE000000 0
073 A010000 0.0000
073 A020000 0.0000
073 B000000 0.0000
073 C000000 0.0000
074 A000000 79031
074 B000000 0
074 C000000 0
074 D000000 0
074 E000000 0
074 F000000 0
074 G000000 0
074 H000000 0
074 I000000 9151246
074 J000000 460
074 K000000 0
074 L000000 69205
074 M000000 1084
074 N000000 9301025
074 O000000 0
074 P000000 13
074 Q000000 0
074 R010000 0
074 R020000 0
074 R030000 0
074 R040000 13562
074 S000000 0
074 T000000 9287450
074 U010000 0
074 U020000 0
074 V010000 0.00
074 V020000 0.00
074 W000000 0.0000
074 X000000 0
074 Y000000 0
075 A000000 0
<PAGE> PAGE 7
075 B000000 9520481
076 000000 0.00
077 A000000 N
078 000000 N
080 A000000 FEDERAL INSURANCE COMPANY
080 C000000 50000
081 A000000 Y
081 B000000 156
082 A000000 Y
082 B000000 100
083 A000000 N
083 B000000 0
084 A000000 N
084 B000000 0
085 A000000 Y
085 B000000 N
086 A010000 0
086 A020000 0
086 B010000 0
086 B020000 0
086 C010000 0
086 C020000 0
086 D010000 0
086 D020000 0
086 E010000 0
086 E020000 0
086 F010000 0
086 F020000 0
088 A000000 N
088 B000000 N
088 C000000 N
088 D000000 N
SIGNATURE BARBARA E. CAMPBELL
TITLE ASSISTANT TREASURER
