OMB APPROVAL OMB Number: 3235-0578 Expires: April 30, 2013 Estimated average burden hours per response..... 5.6 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM N-Q QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS OF REGISTERED MANAGEMENT INVESTMENT COMPANY 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) Terrence J. Cullen, 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, 2010 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 30b1-5 under the Investment Company Act of 1940 (17 CFR 270.30b1-5). 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 7/31/10 (unaudited) Principal Amount Value TAX EXEMPT OBLIGATIONS - 126.9% of Net Assets Alabama - 1.4% 1,000,000 Huntsville-Redstone Village Special Care Facilities Financing Auth., 5.5%, 1/1/28 830,960 4,500,000 Huntsville-Redstone Village Special Care Facilities Financing Auth., 5.5%, 1/1/43 3,453,840 4,284,800 Arizona - 2.1% 5,000,000 Apache County Ind. Dev. Auth., 5.85%, 3/1/28 5,000,400 960,000 Pima County Ind. Dev. Auth., 7.25%, 7/1/31 964,762 500,000 Yavapai County Ind. Dev. Auth., 6.0%, 8/1/33 504,220 6,469,382 California - 8.1% 7,885,000 (a) California State University Rev., RIB, 10.627%, 11/1/39 (144A) 8,225,790 602,382 (b) California Statewide Communities Dev. Auth. Environmental Facilities Rev., 9.0%, 12/1/38 58,732 1,000,000 California Statewide Communities Dev. Auth. Rev., 7.25%, 10/1/38 1,016,150 5,150,000 + Golden State Tobacco Securitization Corp., 7.8%, 6/1/42 6,147,709 7,000,000 + Golden State Tobacco Securitization Corp., 7.875%, 6/1/42 8,370,180 1,000,000 University of California Rev., 5.0%, 5/15/25 1,063,540 655,000 (b) Valley Health System Hosp. Rev., 6.5%, 5/15/25 484,831 25,366,932 Connecticut - 5.1% 10,335,000 (a) Connecticut Health & Edl. Facilities Auth. Rev., RIB, 11.149%, 7/1/42 (144A) 11,853,935 5,000,000 Mohegan Tribe Indians Gaming Auth., 6.25%, 1/1/31 4,111,150 15,965,085 District of Columbia - 3.4% 5,000,000 District of Columbia Tobacco Settlement Financing Corp., 6.5%, 5/15/33 4,793,350 6,000,000 District of Columbia Tobacco Settlement Financing Corp., 6.75%, 5/15/40 5,930,880 10,724,230 Florida - 4.8% 1,700,000 Beacon Lakes Community Dev., 6.9%, 5/1/35 1,681,861 1,000,000 Hillsborough County Ind. Dev. Auth. Rev., 8.0%, 8/15/32 1,143,830 2,390,000 Liberty County Subordinate Rev., 8.25%, 7/1/28 2,307,641 2,500,000 Miami-Dade County Aviation Rev., 5.5%, 10/1/41 2,563,125 1,000,000 St. Johns County Ind. Dev. Auth. Rev., 5.25%, 1/1/ 835,650 2,000,000 St. Johns County Ind. Dev. Auth. Rev., 5.375%, 1/1 1,539,980 5,000,000 Tallahassee Health Facilities Rev., 6.375%, 12/1/3 5,008,650 15,080,737 Georgia - 2.6% 4,240,000 (a) Atlanta Georgia Water & Waste Rev., RIB, 10.628%, 11/1/43 (144A) 4,321,790 500,000 Clayton County Dev. Auth. Rev., 9.0%, 6/1/35 523,945 2,400,000 Fulton County Residential Care Facilities Rev., 5.0%, 7/1/27 1,728,000 1,100,000 Fulton County Residential Care Facilities Rev., 5.125%, 7/1/42 689,150 1,000,000 Rockdale County Dev. Auth. Rev., 6.125%, 1/1/34 939,850 8,202,735 Idaho - 1.6% 5,000,000 Power County Ind. Dev. Corp., 6.45%, 8/1/32 5,030,000 Illinois - 13.5% 2,000,000 (c) Centerpoint Intermodal Center, 7.5%, 6/15/23 (144A 2,025,440 12,000,000 Chicago O'Hare Intl. Airport Special Facility Rev. , Ref. Bonds, 5.5%, 12/1/30 8,898,720 1,000,000 Illinois Fin. Auth. Rev., 6.0%, 11/15/27 779,460 3,865,000 Illinois Fin. Auth. Rev., 6.0%, 8/15/38 3,898,394 2,000,000 Illinois Fin. Auth. Rev., 6.0%, 8/15/39 2,188,140 4,000,000 Illinois Fin. Auth. Rev., 6.0%, 11/15/39 2,790,840 2,500,000 Illinois Fin. Auth. Rev., 6.5%, 4/1/39 2,622,475 4,000,000 Illinois Fin. Auth. Rev., 8.25%, 5/15/45 3,963,000 1,500,000 (b) Illinois Health Facilities Auth. Rev., 6.9%, 11/15 571,800 16,880,000 (d) Metropolitan Pier & Exposition Auth. Dedicated State Tax Rev., 0.0%, 6/15/22 13,036,086 1,685,000 Southwestern Illinois Dev. Auth. Rev., 5.625%, 11/ 1,231,516 42,005,871 Indiana - 3.7% 5,000,000 Indiana Health & Edl. Facility Financing Auth. Hosp. Rev., 5.0%, 2/15/39 4,724,300 4,300,000 Indiana State Dev. Fin. Auth. Rev., 5.75%, 10/1/11 4,379,034 2,570,000 Vigo County Hosp. Auth. Rev., 5.8%, 9/1/47 (144A) 2,352,193 11,455,527 Louisiana - 2.0% 1,500,000 Louisiana Local Government Environmental Facilities Rev., 6.75%, 11/1/32 1,551,390 5,000,000 Louisiana Public Facilities Auth. Rev., 5.5%, 5/15 4,681,300 6,232,690 Massachusetts - 6.3% 5,000,000 Massachusetts Dev. Fin. Agency Rev., 5.75%, 1/1/42 5,573,700 2,360,000 Massachusetts Dev. Fin. Agency Rev., 7.1%, 7/1/32 2,161,359 1,000,000 Massachusetts Edl. Financing Auth. Rev., 6.0%, 1/1 1,063,530 3,500,000 Massachusetts Health & Edl. Facilities Auth. Rev., 6.25%, 7/1/22 3,551,835 2,500,000 Massachusetts Health & Edl. Facilities Auth. Rev., 6.5%, 1/15/38 2,264,175 5,000,000 Massachusetts Health & Edl. Facilities Auth. Rev., 6.75%, 10/1/33 4,990,650 19,605,249 Michigan - 3.4% 935,000 Doctor Charles Drew Academy, 5.7%, 11/1/36 580,747 1,340,000 Flint Michigan Hosp. Building Auth. Rev., 5.25%, 7 1,318,238 1,500,000 John Tolfree Health System Corp., 6.0%, 9/15/23 1,275,015 2,000,000 Michigan State Hosp. Fin. Auth. Rev., 5.5%, 8/15/2 1,919,960 5,830,000 Michigan Tobacco Settlement Fin. Auth., 6.0%, 6/1/ 4,207,686 1,450,000 Star Intl. Academy Certs. of Participation, 6.125% 1,390,347 7,720,000 (e)(g)Wayne Charter Escrow, 0.0%, 12/1/15 0 10,691,993 Minnesota - 0.9% 1,675,000 Duluth Econ. Dev. Auth. Health Care Facilities Rev., 7.25%, 6/15/32 1,713,659 1,000,000 Minneapolis & Saint Paul Housing & ReDev. Auth. Rev., 5.25%, 8/15/35 1,016,370 2,730,029 Mississippi - 1.0% 3,000,000 Mississippi Business Fin. Corp. Pollution Control Rev., 5.9%, 5/1/22 2,996,400 Montana - 0.1% 1,600,000 (b) Two Rivers Auth., Inc. Correctional Facility Improvement Rev., 7.375%, 11/1/27 224,096 Nebraska - 0.2% 2,000,000 Grand Island Solid Waste Disposal Facilities Rev., 603,080 Nevada - 0.0% 2,000,000 (b) Nevada State Dept. of Business & Industry, 7.25%, 10,000 New Jersey - 11.9% 2,000,000 New Jersey Econ. Dev. Auth. Rev., 6.25%, 9/15/19 1,963,240 13,350,000 New Jersey Econ. Dev. Auth. Rev., 6.25%, 9/15/29 12,713,205 6,150,000 (c) New Jersey Econ. Dev. Auth. Rev., 7.0%, 11/15/30 6,160,701 10,370,000 New Jersey Transportation Trust Fund Auth., 0.0%, 4,374,377 10,000,000 + Tobacco Settlement Financing Corp., 6.75%, 6/1/39 11,725,800 36,937,323 New Mexico - 1.2% 1,500,000 Otero County New Mexico Project Rev., 6.0%, 4/1/23 1,274,220 2,960,000 Otero County New Mexico Project Rev., 6.0%, 4/1/28 2,399,169 3,673,389 New York - 8.4% 2,500,000 Albany New York Ind. Dev. Agency Civic Facilities Rev., 5.25%, 11/15/27 2,477,375 3,000,000 Dutchess County Ind. Dev. Agency Rev., 7.5%, 3/1/2 2,992,560 2,000,000 Hempstead Local Dev. Corp. Rev. Bonds, 5.75%, 7/1/ 2,103,840 2,250,000 Nassau County New York Ind. Dev. Agency Rev., 6.7% 2,238,030 990,000 New York City Ind. Dev. Agency, 6.9%, 8/1/24 880,595 2,000,000 New York City Ind. Dev. Agency, 7.625%, 12/1/32 2,021,880 1,000,000 New York State Dormitory Auth. Rev., 6.125%, 12/1/ 1,008,010 7,040,000 (a) New York State Dormitory Auth. Rev., RIB, 12.596%, 9,414,522 3,000,000 Suffolk County Ind. Dev. Agency, 7.25%, 1/1/30 3,001,680 26,138,492 North Carolina - 3.2% 4,935,000 Charlotte Special Facilities Rev., 5.6%, 7/1/27 4,241,830 5,740,000 Charlotte Special Facilities Rev., 7.75%, 2/1/28 5,757,048 9,998,878 Oklahoma - 1.8% 1,225,000 Tulsa Municipal Airport Rev., 6.25%, 6/1/20 1,144,236 4,350,000 Tulsa Municipal Airport Rev., 7.35%, 12/1/11 4,350,043 5,494,279 Pennsylvania - 7.6% 3,000,000 Allegheny County Hosp. Dev. Auth. Rev., 5.0%, 11/1 2,360,010 1,550,000 Allegheny County Hosp. Dev. Auth. Rev., 5.125%, 5/ 1,423,009 12,300,000 + Allegheny County Hosp. Dev. Auth. Rev., 9.25%, 11/ 12,865,062 1,000,000 Columbia County Hosp. Auth. Health Care Rev., 5.9% 861,360 755,000 Hazleton Health Services Auth. Hosp. Rev., 5.625%, 738,284 1,280,000 Langhorne Manor Borough Higher Ed. & Health Auth. Rev., 7.35%, 7/1/22 657,459 5,000,000 Pennsylvania Econ. Dev. Financing Auth. Solid Waste Disposal Rev., 6.0%, 6/1/31 4,396,000 500,000 Pennsylvania Higher Edl. Facilities Auth. Rev., 5. 500,935 23,802,119 Rhode Island - 1.7% 6,000,000 Central Falls Detention Facilities Rev., 7.25%, 7/ 5,167,500 South Carolina - 1.4% 3,185,000 + South Carolina Jobs Econ. Dev. Auth. Rev., 6.375%, 8/1/34 3,692,848 665,000 + South Carolina Jobs Econ. Dev. Auth. Rev., 6.375%, 8/1/34 775,343 4,468,191 Tennessee - 4.8% 7,000,000 + Johnson City Health & Edl. Facilities Board Hosp. Rev., 7.5%, 7/1/33 7,924,840 2,480,000 Knox County Health, Edl. & Housing FacilitiesBoard Hosp. Rev., 6.375%, 4/15/22 2,665,702 4,600,000 Sullivan County Health, Edl. & Housing, Facilities Board Hosp. Rev. , 5.25%, 9/1/36 4,273,354 14,863,896 Texas - 14.5% 1,345,000 Bexar County Housing Fin. Corp., 8.0%, 12/1/36 1,016,000 1,000,000 Dallas-Fort Worth Intl. Airport Rev., 6.0%, 11/1/1 937,980 4,000,000 Decatur Hosp. Auth. Rev., 7.0%, 9/1/25 4,019,320 769,709 (b) Gulf Coast Ind. Dev. Auth. Rev., 7.0%, 12/1/36 75,047 3,750,000 Houston Airport System Special Facilities Rev., 5.7%, 7/15/29 3,261,862 5,340,000 Lubbock Health Facilities Dev. Corp., 6.625%, 7/1/ 4,983,074 10,000,000 North Texas Tollway Auth. Rev., 5.75%, 1/1/33 10,548,400 2,810,000 (a) Northside Independent School District, RIB, 10.983 3,118,960 2,000,000 Tarrant County Cultural Ed. Facilities Fin. Corp., 1,983,760 1,000,000 Tarrant County Cultural Ed. Facilities Fin. Corp., 1,031,870 1,500,000 Tarrant County Cultural Ed. Facilities Fin. Corp., 1,556,280 7,040,000 (a) Texas State, RIB, 11.832%, 4/1/30 (144A) 8,126,483 5,130,000 Willacy County Local Government Corp. Rev., 6.875% 4,557,697 45,216,733 Utah - 0.2% 800,000 Spanish Fork City Charter School Rev., 5.55%, 11/1 687,520 Vermont - 0.5% 1,500,000 Vermont Edl. & Health Buildings Financing Agency Rev., 6.0%, 10/1/28 1,558,035 Virginia - 0.3% 1,000,000 Peninsula Ports Auth., 6.0%, 4/1/33 1,028,010 Washington - 9.1% 4,710,000 Spokane Public Facilities District Hotel/Motel Tax & Sales, 5.75%, 12/1/27 4,922,798 7,025,000 Tobacco Settlement Auth. Rev., 6.625%, 6/1/32 6,964,163 14,315,000 Washington State General Obligation, 0.0%, 6/1/22 9,096,180 3,795,000 Washington State Health Care Facilities Auth. Rev. 3,932,569 5,000,000 Washington State Housing Fin. Committee Nonprofit Rev., 5.625%, 1/1/27 3,559,700 28,475,410 Wisconsin - 0.1% 2,320,000 (b)(f)Aztalan Wisconsin Exempt Facilities Rev., 7.5%, 5/ 301,600 TOTAL TAX-EXEMPT OBLIGATIONS (Cost $383,443,093) 395,490,211 MUNICIPAL COLLATERALIZED DEBT OBLIGATION - 2.4% of Net Assets 10,000,000 (c)(f)Non-Profit Preferred Funding Trust I,12.0%, 9/15/3 7,457,000 TOTAL MUNICIPAL COLLATERALIZED DEBT OBLIGATION (Cost $10,000,000) 7,457,000 Shares COMMON STOCK - 0.9% of Net Assets 249,158 (g) Delta Air Lines, Inc. 2,959,997 TOTAL COMMON STOCK (Cost $6,612,756) 2,959,997 TAX-EXEMPT MONEY MARKET MUTUAL FUND - 0.8% of Net Assets 2,500,000 BlackRock Liquidity Funds MuniFund Portfolio 2,500,000 TOTAL TAX-EXEMPT MONEY MARKET MUTUAL FUND (Cost $2,500,000) 2,500,000 TOTAL INVESTMENTS IN SECURITIES - 131.0% (Cost $402,555,849)(h)(i) 408,407,208 OTHER ASSETS AND LIABILITIES 1.4% 4,285,240 PREFERRED SHARES AT REDEMPTION VALUE, INCLUDING DIVIDENDS PAYABLE - (32.4)% -101,004,135 NET ASSETS APPLICABLE TO COMMON SHAREOWNERS - 100.0% 311,688,313 RIB Residual Interest Bonds NR Security not rated by S&P or Moody's. (144ASecurity 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, 2010 the fair value of these securities amounted to $57,583,633, or 18.5% of et assets applicable to common shareowners. + Prerefunded bonds have been collateralized by U.S. Treasury or U.S. Government Agency securities 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 coupon rate at July 31, 2010. (b) Security is in default and is non-income producing. (c) The interest rate is subject to change periodically. The interest rate shown is the coupon rate at July 31, 2010. (d) Debt obligation initially issued at one coupon which converts to a higher coupon rate at a specific date. The rate shown is the coupon rate at July 31, 2010. (e) Security is valued using fair value methods (other than prices supplied by independent pricing services) . (f) Indicates a security that has been deemed illiquid. The aggregate cost of illiquid securities is $12,320,000. The aggregate fair value is $7,758,600, or 2.5% of the total net assets applicable to common shareowners. (g) Non-income producing. (h) The concentration of investments by type of obligation/market sector is as follows: Insured: NATL-RE 7% AMBAC 2 MBIA 1 FSA 1 PSF 1 ACA 0 Rev. Bonds: Health Rev. 32 Airport Rev. 14 Tobacco Rev. 12 Other Rev. 12 Ed. Rev. 4 Dev. Rev. 4 Facilities Rev. 4 Pollution Control Rev. 4 Transportation Rev. 3 Gaming Rev. 1 Housing Rev. 0 Utilities Rev.* 0 Total 100% * Amount is less than 0.1% (i) At July 31, 2010, the net unrealized gain on investments based on cost for federal income tax purposes of $400,500,819 was as follows: Aggregate gross unrealized gain for all investment there is an excess of value over tax cost 34,821,521 Aggregate gross unrealized loss for all investments in which there is an excess of tax cost over value (26,915,132) Net unrealized gain 7,906,389 For financial reporting purposes net unrealized gain on investments was $5,581,359 'and cost of investments aggregated $402,555,849. Purchases and sales of securities (excluding temporary cash investments $8,920,250 and $7,749,255, respectively. Various inputs are used in determining the value of the Fund's investments. These inputs are summarized in the three broad levels listed below. Highest priority is given to Level 1 inputs and lowest priority is given to Level 3. Level 1 - quoted prices in active markets for identical securities Level 2 - other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risk, etc.) Level 3 - significant unobservable inputs (including the Fund's own assumptions in determining fair value of investments) The following is a summary of the inputs used as of June 30, 2010, in valuing the Fund's assets: Level 1 Level 2 Level 3 Total Tax Exempt Obligations $0 $395,490,211 $ 0 $395,490,211 Municipal collateralized Debt Obligation 7,457,000 0 7,457,000 Common Stocks 2,959,997 0 0 2,959,997 Tax-exempt Money Market Mutual Fund 2,500,000 0 0 2,500,000 Total $5,459,997 $402,947,211 0 $408,407,208 ITEM 2. CONTROLS AND PROCEDURES. (a) Disclose the conclusions of the registrant's principal executive and principal financial officers, or persons performing similar functions, regarding 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 the evaluation of these controls and procedures required by Rule 30a-3(b) under the Act (17 CFR 270.30a-3(b))) and Rule 13a-15(b) or 15d-15(b) under the Exchange Act (17 CFR 240.13a-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 CFR 270.30a-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(a) under the Act (17 CFR 270.30a-2(a)). 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 29, 2010 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 29, 2010 By (Signature and Title)* /s/ Mark Bradley Mark Bradley, Treasurer Date September 29, 2010 * Print the name and title of each signing officer under his or her signature.