Label

Element

Value

MFS SERIES TRUST IV | MFS® Mid Cap Growth Fund

Risk/Return:

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Supplement [Text Block]

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SUPPLEMENT TO PROSPECTUS

The date of this supplement is September 27, 2013.

For Certain MFS® Funds:

Risk/Return [Heading]

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MFS® Mid Cap Growth Fund

Expense Narrative [Text Block]

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Effective immediately, in the second paragraph of the sub-section entitled “Fees and Expenses” beneath the main heading “Summary of Key Information,” the reference to the page number of the “Waivers of Sales Charges” is replaced by reference to page H-1 of the fund’s Statement of Additional Information (“SAI”).