OMB APPROVAL OMB Number: 3235-0578 Expires: April 30, 2010 Estimated average burden hours per response..... 10.5 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM N-Q CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT INVESTMENT COMPANIES Investment Company Act file number 811-21321 Pioneer Municipal High Income Trust (Exact name of registrant as specified in charter) 60 State Street, Boston, MA 02109 (Address of principal executive offices) (ZIP code) Dorothy E. Bourassa, Pioneer Investment Management, Inc., 60 State Street, Boston, MA 02109 (Name and address of agent for service) Registrant's telephone number, including area code: (617) 742-7825 Date of fiscal year end: April 30 Date of reporting period: July 31, 2007 Form N-Q is to be used by management investment companies, other than small business investment companies registered on Form N-5 (239.24 and 274.5 of this chapter), to file reports with the Commission, not later than 60 days after close of the first and third fiscal quarters, pursuant to Rule 30b1-5under the Investment Company Act of 1940 (17 CFR 270.30b-5). The Commission may use the information provided on Form N-Q in its regulatory, disclosure review, inspection, and policymaking roles. A registrant is required to disclose the information specified by Form N-Q, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-Q unless the Form displays a currently valid Office of Management and Budget ("OMB") control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. ss. 3507. ITEM 1. Schedule of Investments. Pioneer Municipal High Income Trust SCHEDULE OF INVESTMENTS 7/31/07 (unaudited) Principal Amount ($) Value ($) TAX EXEMPT OBLIGATIONS - 121.4% Alabama - 1.3% 1,500,000 Camden Alabama Industrial Development Board, 6.125%, 1,612,995 1,000,000 Huntsville-Redstone Village Special Care Facilities 971,300 2,000,000 Huntsville-Redstone Village Special Care Facilities 1,904,620 4,488,915 Arizona - 5.6% 5,000,000 Apache County Industrial Development Authority, 5.85 5,002,000 5,000,000 Apache County Industrial Development Authority, 5.87 5,002,100 7,000,000(a)Downtown Phoenix Hotel Corp., RIB, 6.176%, 7/1/40 (1 7,553,560 1,000,000 Pima County Industrial Development Authority, 7.25%, 1,085,170 500,000 Yavapai County Industrial Development Authority, 6.0 529,095 19,171,925 California - 10.7% 7,270,000 California State General Obligation, 5.25%, 2/1/28 7,620,123 5,000,000 California Statewide Communities Development Authori 5,014,300 5,150,000 + Golden State Tobacco Securitization Corp., 7.8%, 6/1 6,178,970 7,000,000 + Golden State Tobacco Securitization Corp., 7.875%, 6 8,423,310 2,000,000 San Diego Unified School District, 5.0%, 7/1/25 2,064,500 2,500,000 University of California Revenue, 5.0%, 5/15/25 2,583,450 5,000,000 Valley Health System Hospital Revenue, 6.5%, 5/15/25 5,013,800 36,898,453 Connecticut - 1.5% 5,000,000 Mohegan Tribe Indians Gaming Authority, 6.25%, 1/1/3 5,251,300 Delaware - 0.4% 765,000 Sussex County Delaware Revenue, 5.9%, 1/1/26 771,311 600,000 Sussex County Delaware Revenue, 6.0%, 1/1/35 607,866 1,379,177 District of Columbia - 3.5% 5,000,000 District of Columbia Tobacco Settlement Financing Co 5,773,300 6,000,000 District of Columbia Tobacco Settlement Financing Co 6,411,780 12,185,080 Florida - 3.0% 2,000,000 Beacon Lakes Community Development, 6.9%, 5/1/35 2,150,840 1,000,000 St. Johns County Industrial Development Authority Re 986,260 2,000,000 St. Johns County Industrial Development Authority Re 1,985,620 5,000,000 Tallahassee Health Facilities Revenue, 6.375%, 12/1/ 5,219,150 10,341,870 Guam - 1.4% 5,000,000 Northern Mariana Islands, 5.0%, 10/1/22 4,947,300 Georgia - 2.7% 4,240,000(a)Atlanta Georgia Water & Waste Revenue, RIB, 6.271%, 4,604,470 2,400,000 Fulton County Residential Care Facilities Revenue, 5 2,311,968 2,600,000 Fulton County Residential Care Facilities Revenue, 5 2,499,900 9,416,338 Idaho - 1.5% 5,000,000 Power County Industrial Development Corp., 6.45%, 8/ 5,249,950 Illinois - 5.7% 1,000,000 Centerpoint Intermodal Center, 8.0%, 6/15/23 (144A) 1,007,640 2,000,000 Chicago Illinois O'Hare International Airport Revenu 2,056,640 1,000,000 Illinois Finance Authority Revenue, 6.0%, 11/15/27 1,037,360 1,000,000 Illinois Finance Authority Revenue, 6.0%, 11/15/39 1,032,220 1,500,000 Illinois Health Facilities Authority Revenue, 6.9%, 1,635,900 16,880,00(b)Metropolitan Pier & Exposition Authority Dedicated S 11,132,866 1,800,000 Southwestern Illinois Development Authority Revenue, 1,801,116 19,703,742 Indiana - 1.6% 1,000,000 Indiana State Development Finance Authority Revenue, 1,020,370 4,300,000 Indiana State Development Finance Authority Revenue, 4,405,006 5,425,376 Massachusetts - 10.5% 4,000,000 Massachusetts Bay Transportation Authority, 5.0%, 7/ 4,315,520 1,335,000 Massachusetts Health & Educational Facilities Author 1,369,123 7,050,000 Massachusetts Health & Educational Facilities Author 7,319,733 3,500,000 Massachusetts Health & Educational Facilities Author 3,741,115 5,000,000 Massachusetts Health & Educational Facilities Author 5,363,100 9,810,000(a)Massachusetts State Development Finance Agency, RIB, 10,755,684 3,055,000 Massachusetts State Housing Finance Agency, 5.25%, 1 3,086,864 35,951,139 Michigan - 2.5% 950,000 Doctor Charles Drew Academy, 5.7%, 11/1/36 958,075 1,500,000 John Tolfree Health System Corp., 6.0%, 9/15/23 1,521,570 2,000,000 Michigan State Hospital Finance Authority Revenue, 5 1,950,060 4,010,000 Michigan State Hospital Finance Authority Revenue, 6 4,011,083 7,720,000 Wayne Charter County Special Airport Facilities Reve 0 8,440,788 Minnesota - 0.5% 1,675,000 Duluth Economic Development Authority Health Care Fa 1,827,978 Mississippi - 0.9% 3,000,000 Mississippi Business Finance Corp. Pollution Control 3,028,980 Montana - 0.5% 1,600,000 Two Rivers Authority, Inc. Correctional Facility Imp 1,633,072 Nevada - 2.2% 1,000,000 Clark County Industrial Development Revenue, 5.45%, 1,030,470 4,600,000 Clark County Industrial Development Revenue, 5.5%, 1 4,472,304 2,000,000 Nevada State Department of Business & Industry, 7.25 2,029,960 7,532,734 New Hampshire - 0.9% 3,000,000 Manchester School Facilities Revenue, 5.125%, 6/1/28 3,121,620 New Jersey - 10.1% 2,000,000 New Jersey Economic Development Authority Revenue, 6 2,057,240 13,350,000 New Jersey Economic Development Authority Revenue, 6 13,732,077 1,000,000 New Jersey Economic Development Authority Revenue, 6 1,026,690 6,150,000 New Jersey Economic Development Authority Revenue, 7 6,493,293 10,000,00 + Tobacco Settlement Financing Corp., 6.75%, 6/1/39 11,457,800 34,767,100 New Mexico - 0.4% 1,350,000 + Santa Fe Educational Facilities Revenue, 5.75%, 10/1 1,501,646 New York - 10.8% 2,000,000 New York City Industrial Development Agency, 5.375%, 2,048,680 12,990,000 New York City Industrial Development Agency, 6.9%, 8 13,014,551 5,000,000 New York City Trust Cultural Resources Revenue, 5.12 5,189,850 7,040,000(a)New York State Dormitory Authority Revenue, RIB, 6.4 8,355,565 2,000,000 Suffolk County Industrial Development Agency, 7.25%, 2,086,400 6,000,000 Triborough Bridge & Tunnel Authority Revenue, 5.25%, 6,314,160 37,009,206 North Carolina - 2.6% 4,030,000 Charlotte North Carolina Special Facilities Revenue, 4,016,379 4,600,000 Charlotte North Carolina Special Facilities Revenue, 4,856,726 8,873,105 Oklahoma - 6.2% 3,000,000 + Oklahoma Development Finance Authority Revenue, 5.62 3,132,660 8,000,000 + Oklahoma Development Finance Authority Revenue, 5.62 8,353,760 4,100,000 Tulsa Municipal Airport Revenue, 5.65%, 12/1/35 4,115,949 1,225,000 Tulsa Municipal Airport Revenue, 6.25%, 6/1/20 1,225,576 4,350,000 Tulsa Municipal Airport Revenue, 7.35%, 12/1/11 4,357,178 21,185,123 Pennsylvania - 6.6% 3,000,000 Allegheny County Hospital Development Authority Reve 2,812,950 1,550,000 Allegheny County Hospital Development Authority Reve 1,549,938 12,300,00 + Allegheny County Hospital Development Authority Reve 14,530,236 1,000,000 Columbia County Hospital Authority Health Care Reven 898,480 1,000,000 Hazleton Health Services Authority Hospital Revenue, 986,890 1,280,000 Langhorne Manor Borough Higher Education & Health Au 1,298,304 500,000 Pennsylvania Higher Educational Facilities Authority 513,545 22,590,343 Rhode Island - 1.3% 4,000,000 Central Falls Detention Facilities Revenue, 7.25%, 7 4,429,240 South Carolina - 1.9% 5,185,000 + South Carolina Jobs Economic Development Authority R 5,844,999 665,000 + South Carolina Jobs Economic Development Authority R 747,945 6,592,944 Tennessee - 3.7% 7,000,000 Johnson City Health & Educational Facilities Board H 7,981,610 4,480,000 Knox County Health Educational & Housing Facilities 4,553,158 12,534,768 Texas - 10.7% 1,345,000 Bexar County Housing Finance Corp., 8.0%, 12/1/36 1,416,164 1,000,000 Dallas-Fort Worth International Airport Revenue, 6.0 1,000,440 5,000,000 Dallas-Fort Worth International Airport Revenue, 6.1 5,004,050 4,000,000 Decatur Hospital Authority Revenue, 7.0%, 9/1/25 4,318,640 1,000,000 + Georgetown Health Facilities Development Corp., 6.25 1,065,620 2,000,000 Gulf Coast Industrial Development Authority Revenue, 2,106,080 3,750,000 Houston Airport System Special Facilities Revenue, 5 3,778,200 5,340,000 Lubbock Health Facilities Development Corp., 6.625%, 5,556,857 2,450,000(a)Northside Independent School District, RIB, 6.683%, 2,721,019 500,000 Sabine River Authority Pollution Control Revenue, 6. 526,080 7,040,000(a)Texas State, RIB, 6.153%, 4/1/30 (144A) 7,762,234 1,365,000 Willacy County Local Government Corp. Revenue, 6.0%, 1,370,296 36,625,680 Utah - 0.2% 800,000 Spanish Fork City Charter School Revenue, 5.55%, 11/ 805,816 Vermont - 0.5% 1,500,000 Vermont Educational & Health Buildings Financing Age 1,634,205 Virginia - 1.5% 1,000,000 Peninsula Ports Authority, 6.0%, 4/1/33 1,045,070 4,000,000 + Pocahontas Parkway Association of Virginia Toll Road 4,149,680 5,194,750 Washington - 7.3% 4,710,000 Spokane Public Facilities District Hotel/Motel Tax & 5,101,118 7,025,000 Tobacco Settlement Authority Revenue, 6.625%, 6/1/32 7,548,081 14,315,000 Washington State General Obligation, 0.0%, 6/1/22 7,259,852 5,000,000 Washington State Housing Finance Committee Nonprofit 5,092,650 25,001,701 Wisconsin - 0.7% 2,400,000 Aztalan Wisconsin Exempt Facilities Revenue, 7.5%, 5 2,375,592 TOTAL TAX-EXEMPT OBLIGATIONS (Cost $376,484,330) 417,116,956 MUNICIPAL COLLATERALIZED DEBT OBLIGATION - 2.9% of Net Assets 10,000,00(c)Non-Profit Preferred Funding Trust I, Series E, 12.5 9,899,800 TOTAL MUNICIPAL COLLATERALIZED DEBT OBLIGATION (Cost $10,000,000) 9,899,800 Shares COMMON STOCK - 0.8% of Net Assets 159,872 Northwest Airlines Corp. 2,786,569 TOTAL COMMON STOCK (Cost $6,612,756) 2,786,569 TAX-EXEMPT MONEY MARKET MUTUAL FUND - 2.7% of Net Assets 9,213,574 BlackRock Liquidity Funds MuniFund Portfolio 9,213,574 TOTAL TAX-EXEMPT MONEY MARKET MUTUAL FUND (Cost $9,213,574) 9,213,574 TOTAL INVESTMENTS IN SECURITIES - 127.8% (Cost $402,310,660) (d)(e) 439,016,899 OTHER ASSETS AND LIABILITIES - 1.6% 5,450,496 PREFERRED SHARES AT REDEMPTION VALUE, INCLUDING DIVIDENDS PAYABLE - (29.4)% (101,061,645) NET ASSETS APPLICABLE TO COMMON SHAREOWNERS - 100.0% 343,405,750 . RIB Residual Interest Bonds NR Security not rated by S&P or Moody's. (144A) Security is exempt from registration under Rule 144A of the Securities Act of 1933. Such securities may be resold normally to qualified institutional buyers in a transaction exempt from registration. At July 31, 2007 the value of these securities amounted to $58,717,088 or 17.1% of net assets applicable to common shareowners. + Prerefunded bonds have been collateralized by U.S. Treasury securities or U.S. Government Agencies which are held in escrow to pay interest and principal on the tax exempt issue and to retire the bonds in full at the earliest refunding date. (a) The interest rate is subject to change periodically and inversely based upon prevailing market rates. The interest rate shown is the rate at July 31, 2007. (b) Debt obligation initially issued at one coupon which converts to a higher coupon at a specific date. The rate shown is the rate at July 31, 2007. (c) The interest rate is subject to change periodically. The interest rate shown is the rate at July 31, 2007. (d) The concentration of investments by type of obligation/market sector is as follows: Insured 13.5 General Obligation 6.9 Revenue Bonds: Health Revenue 25.5 Airport Revenue 14.5 Tobacco Revenue 10.4 Education Revenue 4.8 Pollution Control Revenue 4.5 Development Revenue 4.3 Other Revenue 3.3 Power Revenue 2.7 Housing Revenue 2.6 Transportation Revenue 2.6 Facilities Revenue 2.4 Gaming Revenue 1.2 School District Revenue 0.6 Utilities Revenue 0.2 100.0 (e) At July 31, 2007, the net unrealized gain on investments based on cost for federal income tax purposes of $400,670,193 was as follows: Aggregate gross unrealized gain for all investments 44,237,635 there is an excess of value over tax cost Aggregate gross unrealized loss for all investments (5,890,929) there is an excess of tax cost over value 38,346,706 Net unrealized gain For financial reporting purposes net unrealized gain on investments was $36,706,239 and cost of investments aggregated $402,310,660. ITEM 2. CONTROLS AND PROCEDURES. (a) Disclose the conclusions of the registrant's principal executive officer or officers and principal financial officer or officers, or persons performing similar functions, about the effectiveness of the registrant's disclosure controls and procedures (as defined in Rule 30a-3(c) under the Act (17 CFR 270.30a-3(c))) as of a date within 90 days of the filing date of the report that includes the disclosure required by this paragraph, based on their evaluation of these controls and procedures required by Rule 30a-3(b) under the Act (17 CFR270.30a-3(b))) and Rule 13a-15(b) or 15d-15(b) under the Exchange Act (17 CFR240.13a-15(b) or 240.15d-15(b)). The registrant's principal executive officer and principal financial officer have concluded that the registrant's disclosure controls and procedures are effective based on their evaluation of these controls and procedures as of a date within 90 days of the filing date of this report. (b) Disclose any change in the registrant's internal controls over financial reporting (as defined in Rule 30a-3(d) under the Act (17 CFR270.30a-3(d)) that occurred during the registrant's last fiscal quarter that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting. There were no significant changes in the registrant's internal control over financial reporting that occurred during the second fiscal quarter of the period covered by this report that have materially affected, or are reasonably likely to materially affect, the registrant's internal control over financial reporting. ITEM 3. EXHIBITS. (a) A separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2 under the Act (17 CFR 270.30a-2). Filed herewith. SIGNATURES [See General Instruction F] Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized. (Registrant) Pioneer Municipal High Income Trust By (Signature and Title)* /s/ John F. Cogan, Jr. John F. Cogan, Jr, President Date September 28, 2007 Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated. By (Signature and Title)* /s/ John F. Cogan, Jr. John F. Cogan, Jr., President Date September 28, 2007 By (Signature and Title)* /s/ Vincent Nave Vincent Nave, Treasurer Date September 28, 2007 * Print the name and title of each signing officer under his or her signature.