<PAGE>
MFS(R) RESEARCH FUND
Supplement to the February 1, 1998 Prospectus and Statement of Additional
Information
The "Expense Summary" section of the Fund's Prospectus is hereby
revised as follows:
1. EXPENSE SUMMARY
<TABLE>
<S> <C> <C> <C> <C>
Shareholder Transaction Expenses:
Class A Class B Class C
Maximum Initial Sales Charge Imposed on Purchases
of Fund Shares (as a percentage of offering price)......................... 5.75% 0.00% 0.00%
Maximum Contingent Deferred Sales Charge (as a percentage
of original purchase price or redemption proceeds,
as applicable)............................................................. See Below(1) 4.00% 1.00%
Annual Operating Expenses of the Fund (as a percentage of average daily net
assets):
Management Fees.............................................................. 0.43% 0.43% 0.43%
Rule 12b-1 Fees.............................................................. 0.35%(2) 1.00%(3) 1.00%(3)
Other Expenses(4)............................................................ 0.27% 0.27% 0.27%
Total Operating Expenses..................................................... 1.05% 1.70% 1.70%
</TABLE>
- -----------------------------
(1) Purchases of $1 million or more and certain purchases by retirement plans
are not subject to an initial sales charge; however, a contingent deferred
sales charge (a "CDSC") of 1% will be imposed on such purchases in the
event of certain redemption transactions within 12 months following such
purchases (see "Information Concerning Shares of the Fund - Purchases"
below).
(2) The Fund has adopted a distribution plan for its shares in accordance with
Rule 12b-1 under the Investment Company Act of 1940, as amended (the "1940
Act") (the "Distribution Plan"), which provides that it will pay
distribution/service fees aggregating up to (but not necessarily all of)
0.35% per annum of the average daily net assets attributable to Class A
shares. The 35% per annum distribution/service fee is reduced to 0.25% per
annum for shares purchased prior to March 1, 1991. Distribution expenses
paid under this Plan, together with the initial sales charge, may cause
long-term shareholders to pay more than the maximum sales charge that would
have been permissible if imposed entirely as an initial sales charge (see
"Information Concerning Shares of the Fund - Distribution Plan" below).
(3) The Fund's Distribution Plan provides that it will pay distribution/service
fees aggregating up to (but not necessarily all of) 1.00% per annum of the
average net assets attributable to Class B shares and Class C shares
respectively. Distribution expenses paid under the Distribution Plan with
respect to Class B or Class C shares, together with any CDSC payable upon
redemption of Class B and Class C shares, may cause long-term shareholders
to pay more than the maximum sales charge that would have been permissible
if imposed entirely as an initial sales charge (see "Information Concerning
Shares of the Fund Distribution Plan" below).
(4) The Fund has an expense offset arrangement which reduces the Fund's
custodian fee based upon the amount of cash maintained by the Fund with its
custodian and dividend disbursing agent, and may enter into other such
arrangements and directed brokerage arrangements (which would also have the
effect of reducing the Fund's expenses). Any such fee reductions are not
reflected under "Other Expenses."
Example of Expenses
An investor would pay the following dollar amounts of expenses on a $1,000
investment in the Fund, assuming (a) 5% annual return and (b) redemption at the
end of each of the time periods indicated (unless otherwise noted):
Period Class A Class B Class C
(1) (1)
1 year............. $ 68 $ 57 $ 17 $ 27 $ 17
3 years............ 89 84 54 54 54
5 years............ 112 112 92 92 92
10 years............ 178 183(2) 183(2) 201 201
- -----------------------------
(1) Assumes no redemption.
(2) Class B shares convert to Class A shares approximately eight years after
purchase; therefore, years nine and ten reflect Class A expenses.
<PAGE>
The purpose of the expense table above is to assist investors in
understanding the various costs and expenses that a shareholder of the Fund will
bear directly or indirectly. More complete descriptions of the following Fund
expenses are set forth in the following sections in the Prospectus: (i) varying
sales charges on share purchases - "Information Concerning Shares of the Fund -
Purchases"; (ii) varying CDSCs "Information Concerning Shares of the Fund -
Purchases"; (iii) management fees - "Management of the Fund - Investment
Adviser"; and (iv) Rule 12b-1 (i.e., distribution plan) fees - "Information
Concerning Shares of the Fund - Distribution Plan".
The "Example" set forth above should not be considered a representation
of past or future expenses of the Fund; actual expenses may be greater or less
than those shown.
2. MANAGEMENT OF THE FUND - Investment Adviser
The first paragraph in the section entitled "Management of the Fund -
Investment Adviser" on Page 14 of the Prospectus is revised in its entirety as
follows:
"Investment Adviser - The Adviser manages the Fund pursuant to an
Investment Advisory Agreement dated November 1, 1998 (the "Advisory
Agreement"). Under the Advisory Agreement, the Adviser provides the
Fund with overall investment advisory services. The Fund is currently
managed by a committee comprised of various equity research analysts
employed by the Adviser. For these services and facilities, the Adviser
receives a management fee, computed and paid monthly in an amount of
0.43% of the Fund's average daily net assets. For the fiscal year ended
September 30, 1997, MFS received management fees of $10,295,600 (of
which $9,009,037 was based on average daily net assets and $1,286,563
on gross income), equivalent, on an annualized basis, to 0.34% of the
Fund's average daily net assets. On October 15, 1998, shareholders of
the Fund approved an increase in the Fund's management fee from its
effective fee of 0.34% per annum to 0.43% per annum pursuant to the
Advisory Agreement."
The second paragraph of the section entitled "Management of the Fund -
Investment Adviser" on page 6 of the Statement of Additional Information is
revised in its entirety as follows:
"The Adviser manages the Fund pursuant to an Investment Advisory
Agreement dated November 1, 1998 (the "Advisory Agreement"). Under the
Advisory Agreement, the Adviser provides the Fund with overall
investment advisory services. Subject to such policies as the Trustees
may determine, the Adviser makes investment decisions for the Fund. For
these services and facilities, the Adviser receives a management fee
computed and paid monthly at an annual rate of 0.43% of the Fund's
average daily net assets."
The date of this Supplement is November 1, 1998.
