REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM
To the Trustees of MFS Municipal Series Trust:
In planning and performing our audit of the financial statements
of MFS Municipal Series Trust (comprised of MFS Alabama Municipal
Bond Fund, MFS Arkansas Municipal Bond Fund, MFS California Municipal
Bond Fund, MFS Florida Municipal Bond Fund, MFS Georgia
Municipal Bond Fund, MFS Maryland Municipal Bond Fund, MFS Massachusetts
Municipal Bond Fund, MFS Mississippi Municipal Bond Fund,
MFS New York Municipal Bond Fund, MFS North Carolina Municipal Bond Fund,
MFS Pennsylvania Municipal Bond Fund, MFS South Carolina
Municipal Bond Fund, MFS Tennessee Municipal Bond Fund, MFS Virginia
Municipal Bond Fund, MFS West Virginia Municipal Bond Fund and
MFS Municipal Income Fund) (the Trust) as of and for the year ended
March 31, 2008, in accordance with the standards of the Public
Company Accounting Oversight Board (United States), we considered the
Trusts internal control over financial reporting, including
control 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 Trusts internal control over financial reporting.
Accordingly, we express no such opinion.
The management of the Trust 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 companys
annual or interim financial statements will not be prevented
or detected on a timely basis.
Our consideration of the Trusts 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
(placecountry-regionUnited States). However, we noted no deficiencies
in the Trusts internal control over financial reporting and its
operation, including controls for safeguarding securities, that we
consider to be a material weakness, as defined above, as of March 31, 2008.
This report is intended solely for the information and use of management
and the Board of Trustees of MFS Municipal Series 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.
DELOITTE & TOUCHE LLP
CityplaceBoston, Massachuetts
May 15, 2008