<PAGE>
MFS(R) CORE GROWTH FUND
Supplement dated January 1, 2000 (as revised 8/4/00) to the Current Prospectus
This Supplement describes the fund's class I shares, and it supplements certain
information in the fund's Prospectus dated January 1, 2000. The caption headings
used in this Supplement correspond with the caption headings used in the
Prospectus.
You may purchase class I shares only if you are an eligible institutional
investor, as described under the caption "Description of Share Classes" below.
1. RISK RETURN SUMMARY
Performance Table. The "Performance Table" is intended to indicate some of
the risks of investing in the fund by showing changes in the fund's
performance over time. The table is supplemented as follows:
Average Annual Total Returns as of December 31, 1998
MFS Core Growth Fund 1 Year Life*
------ -----
Class I shares 37.03% 38.32%
Standard & Poor's 500 Composite Index#+ 28.58% 28.23%
Average growth fund++ 23.42% 22.24%
----------------------------
* Fund performance figures are for the period from the commencement of the
Fund's investment operations on January 2, 1996, through December 31,
1998. Index and Lipper average returns are from January 1, 1996.
# The Standard & Poor's 500 Composite Index is a broad based unmanaged but
commonly used measure of common stock total return performance. It is
composed of 500 widely held common stocks listed on the New York Stock
Exchange, American Stock Exchange and over-the-counter market.
+ Source: Standard & Poor's Micropal.
++ Source: Lipper Analytical Services, Inc.
The Core Growth Fund commenced investment operations on January 2, 1996, with
the offering of class A shares and subsequently offered class I shares on
January 2, 1997. Class I share performance includes the performance of the
Fund's class A shares for periods prior to the offering of class I shares. This
blended class I share performance has been adjusted to take into account the
fact that class I shares have no initial sales charge (load). This blended
performance has not been adjusted to take into account differences in class
specific operating expenses. Because operating expenses of class I shares are
lower than those of class A shares, the blended class I share performance is
lower than the performance of class I shares would have been had class I shares
been offered for the entire period.
2. EXPENSE SUMMARY
Expense Table. The "Expense Table" describes the fees and expenses that you
may pay when you buy, redeem and hold shares of the fund. The table is
supplemented as follows:
Annual Fund Operating Expenses (expenses that are deducted from fund
assets):
Core
Growth Fund
Management Fee..................................... 0.75%
Distribution and Service (12b-1) Fee............... 0.00%
Other Expenses..................................... 0.78%
-----
Total Annual Fund Operating Expenses............... 1.53%
Expense Reimbursement............................ (0.35)%(1)
----------
Net Expenses..................................... 1.18%(2)
--------
-----------------------
(1) MFS has contractually agreed, subject to reimbursement, to bear the
fund's expenses such that "Other Expenses" do not exceed 0.40% annually.
The payments made by MFS on behalf of the fund under this arrangement are
subject to reimbursement by the fund to MFS, which will be accomplished
by the payment of an expense reimbursement fee by the fund to MFS
computed and paid monthly at a percentage of the fund's average daily net
assets for its then current fiscal year, with a limitation that
immediately after such payment the fund's "Other Expenses" will not
exceed 0.40% annually. The obligation of MFS to bear the fund's "Other
Expenses" pursuant to this arrangement, and the fund's obligation to pay
the reimbursement fee to MFS, terminates on the earlier of the date on
which payments made by the fund equal the prior payment of such
reimbursable expenses by MFS, or January 1, 2003. MFS may, in its
discretion, terminate this contractual arrangement at an earlier date,
provided that the arrangement will continue until at least January 1,
2001 unless terminated with the consent of the board of trustees which
oversees the fund.
(2) 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. The fund may enter into
other similar arrangements and directed brokerage arrangements, which
would also have the effect of reducing the fund's expenses. "Other
Expenses" do not take into account these expense reductions, and are
therefore higher than the actual expenses of the fund. Had these fee
reductions been taken into account, "Net Expenses" would be lower, and
for class I shares would be 1.15%.
Example of Expenses. The "Example of Expenses" table is intended to help
you compare the cost of investing in the fund with the cost of investing in
other mutual funds. The examples assume that:
o You invest $10,000 in the fund for the time periods indicated and you
redeem your shares at the end of the time periods;
<PAGE>
o Your investment has a 5% return each year and dividends and other
distributions are reinvested; and
o The fund's operating expenses remain the same, except that the fund's
total operating expenses are assumed to be the fund's "Net Expenses"
for the first year, and the fund's "Total Annual Fund Operating
Expenses" for subsequent years (see Expense Table).
The table is supplemented as follows:
Share Class Year 1 Year 3 Year 5 Year 10
----------- ------ ------ ------ -------
Class I Shares $120 $449 $801 $1,794
3 DESCRIPTION OF SHARE CLASSES
The "Description of Share Classes" is supplemented as follows:
If you are an eligible institutional investor (as described below), you may
purchase class I shares at net asset value without an initial sales charge or
CDSC upon redemption. Class I shares do not have annual distribution and service
fees, and do not convert to any other class of shares of the fund.
The following eligible institutional investors may purchase class I shares:
o certain retirement plans established for the benefit of employees of
MFS and employees of MFS' affiliates.
o any fund distributed by MFS, if the fund seeks to achieve its
investment objective by investing primarily in shares of the fund and
other MFS funds.
o any retirement plan, endowment or foundation which:
has, at the time of purchase of class I shares, aggregate assets
of at least $100 million.
invests at least $10 million in class I shares of the fund either
alone or in combination with investments in class I shares of
other MFS Funds (additional investments may be made in any
amount).
MFD may accept purchases from smaller plans, endowments or
foundations or in smaller amounts if it believes, in its sole
discretion, that such entity's aggregate assets will equal or
exceed $100 million, or that such entity will make additional
investments which will cause its total investment to equal or
exceed $10 million, within a reasonable period of time.
o bank trust departments or law firms acting as trustee or manager for
trust accounts which, on behalf of their clients (i) initially invest
at least $100,000 in class I shares of the fund or (ii) have, at the
time of purchase of class I shares, aggregate assets of at least $10
million invested in class I shares of the fund either alone or in
combination with investments in class I shares of other MFS Funds. MFD
may accept purchases that do not meet these dollar qualification
requirements if it believes, in its sole discretion, that these
requirements will be met within a reasonable period of time. Additional
investments may be made in any amount.
o certain retirement plans offered, administered or sponsored by
insurance companies, provided that these plans and insurance companies
meet certain criteria established by MFD from time to time.
4. HOW TO PURCHASE, EXCHANGE AND REDEEM SHARES
The discussion of "How to Purchase, Exchange and Redeem Shares" is supplemented
as follows:
You may purchase, redeem and exchange class I shares only through your MFD
representative or by contacting MFSC (see the back cover of the Prospectus for
address and phone number). You may exchange your class I shares for class I
shares of another MFS Fund (if you are eligible to purchase them) and for shares
of the MFS Money Market Fund at net asset value.
<PAGE>
5. FINANCIAL HIGHLIGHTS
The "Financial Highlights" table is intended to help you understand the fund's
financial performance. It is supplemented as follows:
<TABLE>
<CAPTION>
<S> <C> <C> <C>
Year Ended Year Ended Period Ended
Core Growth Fund August 31, 1999 August 31, 1998 August 31, 1997*
--------------- --------------- ----------------
Per share data (for a share outstanding throughout each period):
Net asset value - beginning of period $ 14.46 $ 15.84 $ 12.99
------- ------- -------
Income from investment operations# -
Net investment income (loss)ss. $ -- $ (0.01) $ 1.50
Net realized and unrealized gain on investments and
foreign currency 7.33 1.26 1.35
------- ------- -------
Total from investment operations $ 7.33 $ 1.25 $ 2.85
------- ------- -------
Less distributions declared to shareholders -
From net investment income $ -- $ (1.20) $ --
From net realized gain on investments and foreign
currency transactions (2.32) (1.43) --
-------- -------- ------
Total distributions declared to shareholders $ (2.32) $ (2.63) $ --
-------- -------- ------
Net asset value - end of period $ 19.47 $ 14.46 $ 15.84
------- ------- -------
Total return 54.40% 8.82% 21.94%++
Ratios (to average net assets)/Supplemental datass.:
Expenses## 0.71% 0.89% 1.48%+
Net investment income (loss) (0.02)% (0.06)% 14.08%+
Portfolio turnover 240% 261% 1,043%
Net assets at end of period (000 omitted) $10,285 $1,415 $1,695
</TABLE>
ss. The investment adviser voluntarily waived its fee for the periods
indicated. If this fee had been incurred by the fund, the net investment
income (loss) per share and the ratios would have been:
<TABLE>
<CAPTION>
<S> <C> <C> <C>
Net investment income (loss) $ (0.14) $ (0.13) $ 1.40
Ratios (to average net assets):
Expenses## 1.46% 1.65% 2.35%+
Net investment income (loss) (0.77)% (0.81)% 13.20%+
</TABLE>
* For the period from the inception of class I shares, January 2, 1997,
through August 31, 1997.
+ Annualized.
++ Not annualized.
# Per share data are based on average shares outstanding.
## 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. The fund's expenses are calculated
without reduction for this expense offset arrangement.
The date of this Supplement is January 1, 2000 (as revised 8/4/00).
