Report of Independent Registered Public Accounting Firm


                To the Shareholders and Board of Trustees of
                        MFS High Yield Municipal Trust

In planning and  performing  our audit of the  financial statements of MFS High
Yield Municipal Trust (the Fund) as of and for the year ended November 30,2010,
in accordance  with the standards of the Public  Company  Accounting  Oversight
Board (United States), we considered the Fund's internal control over financial
reporting,  including controls  over  safeguarding  securities,  as a basis for
designing our auditing  procedures for the purpose of expressing our opinion on
the financial statements and to comply with the requirements of Form N-SAR, but
not for the purpose of expressing an opinion on the effectiveness of the Fund's
internal  control  over  financial reporting.  Accordingly, we express no such
opinion.

The  management of the Fund is  responsible  for  establishing and  maintaining
effective  internal  control  over  financial  reporting.  In  fulfilling  this
responsibility, estimates and judgments by management are required to assess the
expected  benefits and related costs of controls. A company's  internal control
over financial reporting is a process designed to provide reasonable  assurance
regarding  the  reliability of  financial  reporting  and  the  preparation  of
financial statements for external purposes in accordance with generally accepted
accounting  principles. A company's internal control over financial  reporting
includes those policies and  procedures that (1) pertain to the  maintenance of
records  that,  in  reasonable  detail,  accurately  and  fairly  reflect  the
transactions  and  dispositions of the  assets  of  the  company;  (2)  provide
reasonable  assurance  that transactions  are  recorded as  necessary to permit
preparation  of financial statements  in  accordance  with generally  accepted
accounting  principles, and that receipts and  expenditures of the company are
being made only in accordance with authorizations of management and directors of
the company; and (3) provide reasonable assurance regarding prevention or timely
detection of unauthorized acquisition,  use or disposition of a company's assets
that could have a material effect on the financial statements.

Because of its inherent  limitations, internal control over financial reporting
may not prevent or detect misstatements.  Also, projections of any evaluation of
effectiveness to future periods are subject to the risk that controls may become
inadequate  because of changes in  conditions, or that the degree of compliance
with the policies or procedures may deteriorate.

A deficiency in internal control over financial reporting exists when the design
or operation of a control does not allow management or employees, in the normal
course  of  performing   their   assigned  functions,   to  prevent  or  detect
misstatements  on a timely  basis.  A material weakness is a  deficiency,  or a
combination of deficiencies, in internal control over financial reporting, such
that  there is a  reasonable possibility that a material  misstatement  of the
company's  annual or  interim  financial statements  will not be  prevented  or
detected on a timely basis.

Our  consideration of the Fund's internal control over financial  reporting was
for  the  limited  purpose  described  in the  first  paragraph and  would  not
necessarily disclose all deficiencies in internal control that might be material
weaknesses  under  standards   established  by  the  Public Company  Accounting
Oversight Board (United States).However, we noted no deficiencies in the Fund's
internal control over financial reporting and its operation, including controls
over  safeguarding  securities,  that we consider  to be a material weakness as
defined above as of November 30, 2010.

This report is intended solely for the information and use of management and the
Board of  Trustees  of MFS High Yield  Municipal  Trust and the  Securities and
Exchange  Commission and is not intended to be and should not be used by anyone
other than these specified parties.

 ERNST & YOUNG, LLP

Boston, Massachusetts
January 14, 2011