PAGE 1 000 B000000 04/30/2018 000 C000000 0001223026 000 D000000 N 000 E000000 NF 000 F000000 Y 000 G000000 N 000 H000000 N 000 I000000 6.1 000 J000000 A 001 A000000 PIONEER MUNICIPAL HIGH INCOME TRUST 001 B000000 811-21321 001 C000000 6177427825 002 A000000 60 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 AMUNDI PIONEER ASSET MANAGEMENT, INC. 008 B000001 A 008 C000001 801-8255 008 D010001 BOSTON 008 D020001 MA 008 D030001 02109 010 A000001 AMUNDI PIONEER ASSET MANAGEMENT, INC. 010 B000001 801-8255 010 C010001 BOSTON 010 C020001 MA 010 C030001 02109 010 A000002 BROWN BROTHERS HARRIMAN & CO. 010 B000002 812-13314 010 C010002 BOSTON 010 C020002 MA 010 C030002 02110 011 A000001 AMUNDI PIONEER DISTRIBUTOR, INC. 011 B000001 8-41256 011 C010001 BOSTON PAGE 2 011 C020001 MA 011 C030001 02109 011 C040001 1820 011 A000002 UBS INVESTMENT BANK 011 B000002 8-022651 011 C010002 STAMFORD 011 C020002 CT 011 C030002 06901 011 A000003 RBC CAPITAL MARKETS CORP. 011 B000003 8-045411 011 C010003 MINNEAPOLIS 011 C020003 MN 011 C030003 55402 011 C040003 4422 011 A000004 ADVEST, INC. 011 B000004 8-21409 011 C010004 HARTFORD 011 C020004 CT 011 C030004 06103 011 A000005 JANNEY MONTGOMERY SCOTT, LLC 011 B000005 8-462 011 C010005 PHILADELPHIA 011 C020005 PA 011 C030005 19103 011 C040005 1675 011 A000006 MCDONALD INVESTMENTS, INC. 011 B000006 8-30177 011 C010006 CLEVELAND 011 C020006 OH 011 C030006 44114 011 C040006 2603 011 A000007 STIFEL, NICOLAUS & CO., INC. 011 B000007 8-001447 011 C010007 ST. LOUIS 011 C020007 MO 011 C030007 63102 012 A000001 AMERICAN STOCK TRANSFER & TRUST CO. (COMMON) 012 B000001 85-00000 012 C010001 BROOKLYN 012 C020001 NY 012 C030001 11219 012 A000002 DEUTSCHE BANK TRUST COMPANY AMERICAS (PREF) 012 B000002 85-00000 012 C010002 NEW YORK 012 C020002 NY 012 C030002 10005 012 A000003 DELETE 013 A000001 ERNST & YOUNG LLP 013 B010001 BOSTON 013 B020001 MA 013 B030001 02116 PAGE 3 015 A000001 BROWN BROTHERS HARRIMAN & CO. 015 B000001 C 015 C010001 BOSTON 015 C020001 MA 015 C030001 02110 015 E010001 X 018 000000 Y 019 A000000 Y 019 B000000 42 019 C000000 PIONEERFDS 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 J.P. MORGAN SECURITIES LLC 022 B000001 13-3299429 022 C000001 34977 022 D000001 15689 022 A000002 MORGAN STANLEY & CO. LLC 022 B000002 13-2655998 022 C000002 12328 022 D000002 10711 022 A000003 CITIGROUP GLOBAL MARKETS INC 022 B000003 11-2418191 022 C000003 5966 022 D000003 7018 022 A000004 BROWN BROTHERS HARRIMAN & CO 022 B000004 13-4973745 022 C000004 8767 022 D000004 1270 022 A000005 BNY MELLON CAPITAL MARKETS, LLC 022 B000005 23-2384977 022 C000005 8452 022 D000005 1033 022 A000006 WELLS FARGO SECURITIES, LLC 022 B000006 56-2326000 022 C000006 8772 022 D000006 0 022 A000007 ALEXANDER (J) SECURITIES 022 B000007 00-0000000 022 C000007 5686 022 D000007 2375 022 A000008 U.S. BANCORP INVESTMENTS, INC. 022 B000008 41-1233380 PAGE 4 022 C000008 5006 022 D000008 1015 022 A000009 NOMURA SECURITIES INTERNATIONAL, INC. 022 B000009 13-2642206 022 C000009 2995 022 D000009 2498 022 A000010 DAVIDSON SA CO. INC. NY 022 B000010 00-0000000 022 C000010 4500 022 D000010 0 023 C000000 110098 023 D000000 45545 024 000000 N 025 D000001 0 025 D000002 0 025 D000003 0 025 D000004 0 025 D000005 0 025 D000006 0 025 D000007 0 025 D000008 0 026 A000000 Y 026 B000000 Y 026 C000000 N 026 D000000 Y 026 E000000 N 026 F000000 N 026 G010000 N 026 G020000 Y 026 H000000 N 027 000000 N 028 A010000 0 028 A020000 0 028 A030000 0 028 A040000 0 028 B010000 0 028 B020000 0 028 B030000 0 028 B040000 0 028 C010000 0 028 C020000 0 028 C030000 0 028 C040000 0 028 D010000 0 028 D020000 0 028 D030000 0 028 D040000 0 028 E010000 0 028 E020000 0 028 E030000 0 028 E040000 0 PAGE 5 028 F010000 0 028 F020000 0 028 F030000 0 028 F040000 0 028 G010000 0 028 G020000 0 028 G030000 0 028 G040000 0 028 H000000 0 030 A000000 0 030 B000000 0.00 030 C000000 0.00 031 A000000 0 031 B000000 0 032 000000 0 033 000000 0 035 000000 0 036 B000000 0 038 000000 0 042 A000000 0 042 B000000 0 042 C000000 0 042 D000000 0 042 E000000 0 042 F000000 0 042 G000000 0 042 H000000 0 043 000000 0 044 000000 0 045 000000 Y 046 000000 N 047 000000 Y 048 000000 0.600 048 A010000 0 048 A020000 0.000 048 B010000 0 048 B020000 0.000 048 C010000 0 048 C020000 0.000 048 D010000 0 048 D020000 0.000 048 E010000 0 048 E020000 0.000 048 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 PAGE 6 048 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 054 C000000 Y 054 D000000 N 054 E000000 N 054 F000000 N 054 G000000 N 054 H000000 Y 054 I000000 N 054 J000000 Y 054 K000000 N 054 L000000 N 054 M000000 Y 054 N000000 N 054 O000000 N 055 A000000 N 055 B000000 N 056 000000 N 057 000000 N 058 A000000 N 059 000000 Y 060 A000000 Y 060 B000000 Y 061 000000 0 062 A000000 Y 062 B000000 0.0 062 C000000 0.0 062 D000000 0.0 062 E000000 0.0 062 F000000 0.0 062 G000000 0.0 062 H000000 0.0 062 I000000 0.0 062 J000000 0.0 062 K000000 0.0 062 L000000 0.0 062 M000000 0.0 062 N000000 0.0 062 O000000 140.6 062 P000000 0.9 062 Q000000 0.0 062 R000000 0.0 PAGE 7 063 A000000 0 063 B000000 6.6 064 A000000 Y 064 B000000 Y 065 000000 N 066 A000000 N 067 000000 N 068 A000000 N 068 B000000 N 069 000000 N 070 A010000 Y 070 A020000 N 070 B010000 N 070 B020000 N 070 C010000 Y 070 C020000 N 070 D010000 N 070 D020000 N 070 E010000 Y 070 E020000 N 070 F010000 N 070 F020000 N 070 G010000 Y 070 G020000 N 070 H010000 N 070 H020000 N 070 I010000 N 070 I020000 N 070 J010000 Y 070 J020000 Y 070 K010000 Y 070 K020000 N 070 L010000 N 070 L020000 N 070 M010000 N 070 M020000 N 070 N010000 N 070 N020000 N 070 O010000 Y 070 O020000 N 070 P010000 Y 070 P020000 N 070 Q010000 N 070 Q020000 N 070 R010000 N 070 R020000 N 071 A000000 98385 071 B000000 77447 071 C000000 390374 071 D000000 20 072 A000000 12 PAGE 8 072 B000000 20804 072 C000000 0 072 D000000 0 072 E000000 0 072 F000000 2381 072 G000000 142 072 H000000 0 072 I000000 18 072 J000000 7 072 K000000 0 072 L000000 17 072 M000000 13 072 N000000 0 072 O000000 0 072 P000000 0 072 Q000000 0 072 R000000 59 072 S000000 67 072 T000000 0 072 U000000 0 072 V000000 18 072 W000000 225 072 X000000 2947 072 Y000000 0 072 Z000000 17857 072AA000000 0 072BB000000 12146 072CC010000 5201 072CC020000 0 072DD010000 14004 072DD020000 0 072EE000000 0 073 A010000 0.6150 073 A020000 0.0000 073 B000000 0.0000 073 C000000 0.0000 074 A000000 823 074 B000000 0 074 C000000 0 074 D000000 402673 074 E000000 0 074 F000000 0 074 G000000 0 074 H000000 0 074 I000000 0 074 J000000 30 074 K000000 0 074 L000000 6100 074 M000000 148 074 N000000 409774 074 O000000 0 PAGE 9 074 P000000 37 074 Q000000 0 074 R010000 0 074 R020000 0 074 R030000 0 074 R040000 147 074 S000000 124994 074 T000000 284596 074 U010000 22771 074 U020000 0 074 V010000 12.50 074 V020000 0.00 074 W000000 0.0000 074 X000000 3769 074 Y000000 0 075 A000000 0 075 B000000 289902 076 000000 11.25 077 A000000 Y 077 B000000 Y 078 000000 N 080 A000000 ICI MUTUAL INSURANCE CO. 080 C000000 38000 081 A000000 Y 081 B000000 42 082 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 0 087 A010000 COMMON STOCK 087 A020000 723763108 087 A030000 MHI 087 B010000 PREFERRED STOCK - SERIES A 087 B020000 723763207 087 C010000 PREFERRED STOCK - SERIES B PAGE 10 087 C020000 723763306 088 A000000 N 088 B000000 N 088 C000000 N 088 D000000 Y SIGNATURE MARK BRADLEY TITLE TREASURER