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<PAGE> PAGE 2
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<PAGE> PAGE 3
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<PAGE> PAGE 4
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<PAGE> PAGE 5
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<PAGE> PAGE 6
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<PAGE> PAGE 7
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<PAGE> PAGE 8
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<PAGE> PAGE 9
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<PAGE> PAGE 10
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<PAGE> PAGE 11
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<PAGE> PAGE 12
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<PAGE> PAGE 13
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<PAGE> PAGE 14
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<PAGE> PAGE 15
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<PAGE> PAGE 16
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<PAGE> PAGE 17
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<PAGE> PAGE 18
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<PAGE> PAGE 19
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<PAGE> PAGE 20
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<PAGE> PAGE 22
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<PAGE> PAGE 23
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<PAGE> PAGE 24
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SIGNATURE ELLEN M. MOYNIHAN
TITLE ASSISTANT TREASURER
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<PERIOD-TYPE> YEAR
<FISCAL-YEAR-END> AUG-31-1999
<PERIOD-START> SEP-01-1998
<PERIOD-END> AUG-31-1999
<INVESTMENTS-AT-COST> 254461278
<INVESTMENTS-AT-VALUE> 267534180
<RECEIVABLES> 7058005
<ASSETS-OTHER> 2154
<OTHER-ITEMS-ASSETS> 6250
<TOTAL-ASSETS> 274600589
<PAYABLE-FOR-SECURITIES> 2212618
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 57857408
<TOTAL-LIABILITIES> 60070026
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 171850249
<SHARES-COMMON-STOCK> 1643790
<SHARES-COMMON-PRIOR> 744654
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> (22700)
<ACCUMULATED-NET-GAINS> 29630112
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 13072902
<NET-ASSETS> 214530563
<DIVIDEND-INCOME> 196035
<INTEREST-INCOME> 700014
<OTHER-INCOME> 98356
<EXPENSES-NET> (2803260)
<NET-INVESTMENT-INCOME> (1808855)
<REALIZED-GAINS-CURRENT> 36329324
<APPREC-INCREASE-CURRENT> 37191254
<NET-CHANGE-FROM-OPS> 71711723
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 0
<DISTRIBUTIONS-OF-GAINS> 1090227
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 2120776
<NUMBER-OF-SHARES-REDEEMED> (1326970)
<SHARES-REINVESTED> 105330
<NET-CHANGE-IN-ASSETS> 115487320
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 13134433
<OVERDISTRIB-NII-PRIOR> (14911)
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 1185344
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 2809690
<AVERAGE-NET-ASSETS> 158068316
<PER-SHARE-NAV-BEGIN> 7.53
<PER-SHARE-NII> (0.14)
<PER-SHARE-GAIN-APPREC> 4.91
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> (1.29)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 11.01
<EXPENSE-RATIO> 2.07
</TABLE>
<TABLE> <S> <C>
<ARTICLE> 6
<CIK> 0000063068
<NAME> MFS SERIES TRUST IV
<SERIES>
<NUMBER> 044
<NAME> MFS MID CAP GROWTH FUND - CLASS I
<MULTIPLIER> 1
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<INVESTMENTS-AT-VALUE> 267534180
<RECEIVABLES> 7058005
<ASSETS-OTHER> 2154
<OTHER-ITEMS-ASSETS> 6250
<TOTAL-ASSETS> 274600589
<PAYABLE-FOR-SECURITIES> 2212618
<SENIOR-LONG-TERM-DEBT> 0
<OTHER-ITEMS-LIABILITIES> 57857408
<TOTAL-LIABILITIES> 60070026
<SENIOR-EQUITY> 0
<PAID-IN-CAPITAL-COMMON> 171850249
<SHARES-COMMON-STOCK> 162000
<SHARES-COMMON-PRIOR> 119708
<ACCUMULATED-NII-CURRENT> 0
<OVERDISTRIBUTION-NII> (22700)
<ACCUMULATED-NET-GAINS> 29630112
<OVERDISTRIBUTION-GAINS> 0
<ACCUM-APPREC-OR-DEPREC> 13072902
<NET-ASSETS> 214530563
<DIVIDEND-INCOME> 196035
<INTEREST-INCOME> 700014
<OTHER-INCOME> 98356
<EXPENSES-NET> (2803260)
<NET-INVESTMENT-INCOME> (1808855)
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<APPREC-INCREASE-CURRENT> 37191254
<NET-CHANGE-FROM-OPS> 71711723
<EQUALIZATION> 0
<DISTRIBUTIONS-OF-INCOME> 0
<DISTRIBUTIONS-OF-GAINS> 168193
<DISTRIBUTIONS-OTHER> 0
<NUMBER-OF-SHARES-SOLD> 59850
<NUMBER-OF-SHARES-REDEEMED> (35959)
<SHARES-REINVESTED> 18401
<NET-CHANGE-IN-ASSETS> 115487320
<ACCUMULATED-NII-PRIOR> 0
<ACCUMULATED-GAINS-PRIOR> 13134433
<OVERDISTRIB-NII-PRIOR> (14911)
<OVERDIST-NET-GAINS-PRIOR> 0
<GROSS-ADVISORY-FEES> 1185344
<INTEREST-EXPENSE> 0
<GROSS-EXPENSE> 2809690
<AVERAGE-NET-ASSETS> 158068316
<PER-SHARE-NAV-BEGIN> 7.73
<PER-SHARE-NII> (0.04)
<PER-SHARE-GAIN-APPREC> 5.04
<PER-SHARE-DIVIDEND> 0
<PER-SHARE-DISTRIBUTIONS> (1.36)
<RETURNS-OF-CAPITAL> 0
<PER-SHARE-NAV-END> 11.37
<EXPENSE-RATIO> 1.07
</TABLE>
INDEPENDENT AUDITORS' REPORT
To the Trustees and Shareholders of MFS Series Trust IV:
In planning and performing our audits of the financial statements of MFS Series
Trust IV (composed of MFS Government Money Market Fund, MFS Money Market Fund,
MFS Mid Cap Growth Fund, and MFS Municipal Bond Fund) (the "Trust") for the year
ended August 31, 1999 (on which we have issued our reports dated October 7,
1999), 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 generally accepted accounting
principles. 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 are 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
August 31, 1999.
This report is intended solely for the information and use of management, the
Board of Trustees, 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
October 7, 1999
<PAGE>
