INDEPENDENT AUDITORS' REPORT
To the Trustees and Shareholders of MFS Series Trust X:
In planning and performing our audits of the financial statements of MFS Series
Trust X (comprised of MFS Government Mortgage Fund, MFS Concentrated Growth
Fund, MFS European Equity Fund, MFS High Yield Fund and MFS Income Fund) (the
"Trust") for the year ended July 31, 2000 (on which we have issued our reports
dated September 7, 2000), we considered its internal control, including control
activities for safeguarding securities, in order to determine our auditing
procedures for the purpose of expressing our opinions on the financial
statements and to comply with the requirements of Form N-SAR, and not to provide
assurance on the Trust's internal control.
The management of the Trust is responsible for establishing and maintaining
internal control. In fulfilling this responsibility, estimates and judgments by
management are required to assess the expected benefits and related costs of
controls. Generally, controls that are relevant to an audit pertain to the
entity's objective of preparing financial statements for external purposes that
are fairly presented in conformity with accounting principles generally accepted
in the United States of America. Those controls include the safeguarding of
assets against unauthorized acquisition, use or disposition.
Because of inherent limitations in any internal control, misstatements due to
error or fraud may occur and not be detected. Also, projections of any
evaluation of internal control to future periods is subject to the risk that the
internal control may become inadequate because of changes in conditions or that
the degree of compliance with policies or procedures deteriorates.
Our consideration of the Trust's internal control would not necessarily disclose
all matters in internal control that might be material weaknesses under
standards established by the American Institute of Certified Public Accountants.
A material weakness is a condition in which the design or operation of one or
more of the internal control components does not reduce to a relatively low
level the risk that misstatements caused by error or fraud in amounts that would
be material in relation to the financial statements being audited may occur and
not be detected within a timely period by employees in the normal course of
performing their assigned functions. However, we noted no matters involving the
Trust's internal control and its operation, including controls for safeguarding
securities that we consider to be material weaknesses as defined above as of
July 31, 2000.
This report is intended solely for the information and use of management, the
Trustees and Shareholders of MFS Series Trust X, 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
Boston, Massachusetts
September 7, 2000
