Shareholder Proxy Services ------------------------------------------------------------------------------- September 15, 2009 IMPORTANT MATTER REG1 ---- REG 2 ----- REG 3 ----- REG 4 ----- REG 5 ----- REG 6 ----- REG 7 ----- Re: Pioneer Municipal High Income Trust (NYSE: MHI) Cusip: 723763108 Dear Shareholder: Our firm has been retained by Pioneer Municipal High Income Trust to contact you regarding your investment in common shares of the Trust, as of record date July 9, 2009. We have attempted to contact you, but have yet to be successful. Please contact us immediately at 1-800-232-1064 between the hours of 9:00 a.m. and 11:00 p.m., Eastern Standard Time. Thank you in advance for your assistance with this matter. Sincerely, PFred Bonnell Investor Relations Supervisor Shareholder Services The Altman Group ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- "tag id" ------------------------------------------------------------------------------- 60 East 42nd Street, New York, New York 10165