MFS SUN LIFE SERIES TRUST, 485APOS, 1999-08-13

MFS SUN LIFE SERIES TRUST
485APOS, 1999-08-13

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As filed with the Securities and Exchange Commission on August 13, 1999
1933 Act File No. 2-83616
1940 Act File No. 811-3732

===============================================================================

SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
------------------

FORM N-1A
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

POST-EFFECTIVE AMENDMENT NO. 24

AND

REGISTRATION STATEMENT UNDER
THE INVESTMENT COMPANY ACT OF 1940

AMENDMENT NO. 28

MFS/SUN LIFE SERIES TRUST
(Exact Name of Registrant as Specified in Charter)

500 Boylston, Street, Boston, Massachusetts 02116
(Address of Principal Executive Offices)

Registrant's Telephone Number, Including Area Code: (617) 954-5000
Stephen E. Cavan, Massachusetts Financial Services Company
500 Boylston Street, Boston, Massachusetts 02116
(Name and Address of Agent for Service)

Approximate Date of Proposed Public Offering:

It is proposed that this filing will become effective (check appropriate box)

|_| immediately upon filing pursuant to paragraph (b)
|_| on [date] pursuant to paragraph (b)
|_| 60 days after filing pursuant to paragraph (a)(i)
|_| on [date] pursuant to paragraph (a)(i)
|_| 75 days after filing pursuant to paragraph (a)(ii)
|X| on October 27, 1998 pursuant to paragraph (a)(ii) of rule 485.

If appropriate, check the following box:
|_| this post-effective amendment designates a new effective date for a
previously filed post-effective amendment

===============================================================================
<PAGE>
Supplement dated November 1, 1999 to the Current Prospectus

MFS/SUN LIFE SERIES TRUST (THE "TRUST")

This supplement describes a new series of the Trust -- the Strategic Growth
Series -- and supplements certain information in the Trust's Prospectus dated
May 1, 1999. The caption headings used in this Supplement correspond with the
caption headings used in the Prospectus. Information which is not supplemented
applies equally to the Strategic Growth Series.

I. EXPENSE SUMMARY - BEGINNING ON PAGE 1

Expense Table. This table describes the expense that you may pay when you
hold shares of the series. These fees and expenses do not take into account
the fees and expenses imposed under the Variable Contracts through which an
investment in the series is made. The table is supplemented as follows:

Annual Operating Expenses (expenses that are deducted from a series'
assets):

Strategic Growth Series
Management Fee 0.75%
Other Expenses 3.43%
----
Total Annual Series Operating Expenses 4.18%
Fee Waivers/Expense Reimbursement(1) (3.15)%
----
Net Expenses(2) 1.03%
- -----------------------
(1) MFS has contractually agreed to bear the series' expenses such that "Other
Expenses" do not exceed 0.25% annually. This contractual arrangement will
continue until at least May 1, 2000, unless modified with the consent of
the board of trustees, which oversees the series.
(2) The series has an expense offset arrangement which reduces its custodian
fee based upon the amount of cash maintained by the series with its
custodian and dividend disbursing agent. The series may enter into other
similar arrangements and directed brokerage arrangements, which would also
have the effect of reducing the series' expenses. The series expenses do
not take into account these expense reductions, and therefore do not
represent the actual expenses of the series. Had these expense reductions
been taken into account, "Net Expenses" would be 1.00%.

Example of Expenses. The "Example of Expenses" table is intended to help
you compare the cost of investing in the series with the cost of investing
in other mutual funds.

The example assumes that:

o You invest $10,000 in the series for the time periods indicated
and you redeem your shares at the end of the time periods;

o Your investment has a 5% return each year and dividends and other
distributions are reinvested; and

o The series' operating expenses remain the same, except that the
series' total operating expenses are assumed to be the series'
"Net Expenses" for the first year, and the series' "Total Annual
Series Operating Expenses" for subsequent years (see table above).

1
<PAGE>

The table is supplemented as follows:

Although your actual costs may be higher or lower, under these
assumptions your costs would be:

Year 1 Year 3

Strategic Growth Series $102 $979

II. RISK RETURN SUMMARY - BEGINNING ON PAGE 4

This section of the prospectus is supplemented as follows:

27: Strategic Growth Series

Investment Objective. The series' investment objective is capital
appreciation. Approval by the series' shareholders is not required to
modify or change the series' objective.

Principal Investment Strategies. The series invests, under normal market
conditions, at least 65% of its total assets in common stocks and related
securities, such as preferred stocks, bonds, warrants, or rights
convertible into stock and depositary receipts for these securities, of
companies which MFS believes offer superior prospects for growth.

MFS uses a bottom-up, as opposed to a top-down, investment style in
managing the equity-oriented funds (such as the series) it advises. This
means that securities are selected based upon fundamental analysis (such as
an analysis of earnings, cash flows, competitive position and management's
abilities) performed by the series' portfolio manager and MFS' large group
of equity research analysts.

In managing the series, MFS seeks to purchase securities of companies which
MFS considers well-run and poised for growth. MFS looks particularly for
companies which demonstrate:

o a strong franchise, strong cash flows and a recurring revenue stream

o a solid industry position, where there is

potential for high profit margins

substantial barriers to new entry in the industry

o a strong management team with a clearly defined strategy

o a catalyst which may accelerate growth

Consistent with the series' principal investment strategies described
above, the series may invest in foreign securities, and may have exposure
to foreign currencies through its investment in these securities.

Principal Risks of an Investment. The principal risks of investing in the
series and the circumstances reasonably likely to cause the value of your
investment in the series to decline are described below. The share price of
the series generally changes daily based on market conditions and other
factors. Please note that there are many circumstances which could cause
the value of your

2
<PAGE>

investment in the series to decline, and which could prevent the series
from achieving its objective, that are not described here. The principal
risks of investing in the series are:

o Market Risk: This is the risk that the price of a security held by
the series will fall due to changing economic, political or market
conditions, or due to the financial condition of the company which
issued the security.

o Growth Companies: This is the risk that the prices of growth
company securities held by the series, which are the series' principal
investment focus, will fall to a greater extent than the overall
equity markets (e.g., as represented by the Standard and Poor's
Composite 500 Index) due to changing economic, political or market
conditions.

o Foreign Securities: Investments in foreign securities involve
risks relating to political, social and economic developments abroad,
as well as risks resulting from the differences between the
regulations to which U.S. and foreign issuers and markets are subject:

These risks may include the seizure by the government of company
assets, excessive taxation, withholding taxes on dividends and
interest, limitations on the use or transfer of portfolio assets,
and political or social instability.

Enforcing legal rights may be difficult, costly and slow in
foreign countries, and there may be special problems enforcing
claims against foreign governments.

Foreign companies may not be subject to accounting standards or
governmental supervision comparable to U.S. companies, and there
may be less public information about their operations.

Foreign markets may be less liquid and more volatile than U.S.
markets.

Foreign securities often trade in currencies other than the U.S.
dollar, and the series may directly hold foreign currencies and
purchase and sell foreign currencies through forward exchange
contracts. Changes in currency exchange rates will affect the
series' net asset value, the value of dividends and interest
earned, and gains and losses realized on the sale of securities.
An increase in the strength of the U.S. dollar relative to these
other currencies may cause the value of the series to decline.
Certain foreign currencies may be particularly volatile, and
foreign governments may intervene in the currency markets,
causing a decline in value or liquidity in the series' foreign
currency holdings. Forward foreign currency exchange contracts
involve the risk that the party with which the series enters the
contract may fail to perform its obligations to the series.

Bar Chart and Performance Table. The bar chart and performance table are
not included because the series did not have a full calendar year of
performance on December 31, 1998.

III. CERTAIN INVESTMENT STRATEGIES AND RISKS - BEGINNING ON PAGE 76

The series may invest in various types of securities and engage in various
investment techniques and practices which are not the principal focus of
the series and therefore are not described in this Supplement. The types of
securities and investment techniques and practices in which the Series may
engage are identified in Appendix A to this Supplement, and are discussed,
together with their risks, in the Series' Statement of Additional
Information (referred to as the SAI), which you may obtain by contacting
Sun Life Assurance Company of Canada (U.S.) Retirement Products and
Services Division (see the back cover of the prospectus for the address and
phone number).

3
<PAGE>

IV. MANAGEMENT OF THE SERIES - BEGINNING ON PAGE 77

Investment Adviser. Massachusetts Financial Services Company is the series'
investment adviser, and is described in the prospectus.

Portfolio Managers.

This section is supplemented as follows:

Series Portfolio Managers
------ ------------------

Strategic Growth Series S. Irfan Ali, Vice President of MFS,-
and Stephen Pesek, Senior Vice President
of MFS, have been portfolio managers of
the series since its inception. Mr.
Ali has been employed by MFS as a
portfolio manager since 1993 and Mr.
Pesek has been employed by MFS as a
portfolio manager since 1994.

4
<PAGE>

APPENDIX A

Investment Techniques and Practices. In pursing its investment
objective, the series may engage in the following principal and
non-principal investment techniques and practices. Investment
techniques and practices which are the principal focus of the series
are described, together with their risks, in the Risk Return Summary of
this Supplement. Both principal and non-principal investment techniques
and practices are described, together with their risks, in the SAI.

Investment Techniques/Practices
<TABLE>
<CAPTION>
<S> <C> <C>
Symbols |X| Permitted -- Not Permitted
Strategic Growth Series
Debt Securities
Asset-Backed Securities
Collateralized Mortgage Obligations and Multiclass --
Pass-Through Securities
Corporate Asset-Backed Securities --
Mortgage Pass-Through Securities --
Stripped Mortgage-Backed Securities --
Corporate Securities |X|
Loans and Other Direct Indebtedness --
Lower Rated Bonds --
Municipal Bonds --
Speculative Bonds --
U.S. Government Securities |X|
Variable and Floating Rate Obligations --
Zero Coupon Bonds, Deferred Interest Bonds and PIK Bonds |X|
Equity Securities |X|
Foreign Securities Exposure
Brady Bonds --
Depositary Receipts |X|
Dollar-Denominated Foreign Debt Securities |X|
Emerging Markets |X|
Foreign Securities |X|
Forward Contracts |X|
Futures Contracts |X|
Indexed Securities/Structured Products |X|
Inverse Floating Rate Obligations --
Investment in Other Investment Companies
Open-End Funds |X|
Closed-End Funds |X|
Laddering --
Lending of Portfolio Securities |X|
Leveraging Transactions
Bank Borrowings |X|
Mortgage "Dollar-Roll" Transactions --
Reverse Repurchase Agreements |X|
Options
Options on Foreign Currencies |X|
Options on Futures Contracts |X|
Options on Securities |X|
Options on Stock Indices |X|
Reset Options |X|
"Yield Curve" Options |X|
</TABLE>

5
<PAGE>

<TABLE>
<CAPTION>
<S> <C> <C>
Symbols |X| Permitted -- Not Permitted
Strategic Growth Series

Repurchase Agreements |X|
Restricted Securities |X|
Short Sales |X|
Short Sales Against the Box |X|
Short Term Instruments |X|
Swaps and Related Derivative Instruments |X|
Temporary Borrowings |X|
Temporary Defensive Positions |X|
Warrants |X|
"When-issued" Securities |X|
</TABLE>

The date of this Supplement is November 1, 1999.

6
<PAGE>

Supplement dated November 1, 1999 to the Current Statement of
Additional Information
OF
MFS/SUN LIFE SERIES TRUST (THE "TRUST")

This Supplement describes a new series of the Trust -- the Strategic Growth
Series -- and supplements certain information in the Trust's Statement of
Additional Information dated May 1, 1999. The caption headings used in this
Supplement correspond with the caption headings used in the Statement of
Additional Information. Information which is not supplemented applies equally to
the Strategic Growth Series.

1. DEFINITIONS - PAGE 3

This section is supplemented as follows:

The number "27" replaces the number "26" at the end of the first paragraph.

The following item is added at the end of the list of investment options:

"27. Strategic Growth Series"

2. INVESTMENT TECHNIQUES, PRACTICES AND RISKS - BEGINNING ON PAGE 3

This section is supplemented by adding the following disclosure at the end
of the section on page 5:

"25. Strategic Growth Series
Foreign Securities:............... up to (but not including) 20%
Securities Lending:............... 30%"

3. INVESTMENT RESTRICTIONS - BEGINNING ON PAGE 5

This section is supplemented by adding the following disclosure at the end
of the section on page 11:

"(15) Investment Restrictions that Apply Only to the Strategic Growth
Series:

The Strategic Growth Series may not:

(1) Borrow amounts from banks in excess of 33 1/3% of its assets,
including amounts borrowed.

(2) Underwrite securities issued by other persons except insofar as the
Series may technically be deemed an underwriter under the Securities
Act of 1933, as amended (the "1933 Act") in selling a portfolio
security.

(3) Purchase or sell real estate (including limited partnership interests
but excluding securities secured by real estate or interests therein
and securities of companies, such as real estate investment trusts,
which deal in real estate or interests therein), interests in oil, gas
or mineral leases, commodities or commodity contracts (excluding
currencies and any type of option, Futures Contracts and Forward
Contracts) in the ordinary course of its business. The Series reserves
the freedom of action to hold and to sell real estate, mineral leases,
commodities or commodity contracts (including currencies and any type
of option, Futures Contracts and Forward Contracts) acquired as a
result of the ownership of securities.

(4) Issue any senior securities except as permitted by the 1940 Act. For
purposes of this restriction, collateral arrangements with respect to
any type of swap, option, Forward Contracts and Futures Contracts

1
<PAGE>

and collateral arrangements with respect to initial and variation
margin are not deemed to be the issuance of a senior security.

(5) Make loans to other persons. For these purposes, the purchase of
commercial paper, the purchase of a portion or all of an issue of debt
securities, the lending of portfolio securities, or the investment of
the Series' assets in repurchase agreements, shall not be considered
the making of a loan. or

(6) Purchase any securities of an issuer of a particular industry, if as a
result, 25% or more of its gross assets would be invested in
securities of issuers whose principal business activities are in the
same industry (except there is no limitation with respect to
obligations issued or guaranteed by the U.S. Government or its
agencies and instrumentalities and repurchase agreements
collateralized by such obligations).

In addition, the Series has adopted the following nonfundamental policies
which may be changed by the vote of the Series Fund's Board of Trustees without
shareholder approval. The Strategic Growth Series will not:

(1) Invest in illiquid investments, including securities subject to legal
or contractual restrictions on resale or for which there is no readily
available market (e.g., trading in the security is suspended, or, in
the case of unlisted securities, where no market exists), if more than
15% of the Series' assets (taken at market value) would be invested in
such securities. Repurchase agreements maturing in more than seven
days will be deemed to be illiquid for purposes of the Series'
limitation on investment in illiquid securities. Securities that are
not registered under the 1933 Act and sold in reliance on Rule 144A
thereunder, but are determined to be liquid by the Series Fund's Board
of Trustees (or its delegee), will not be subject to this 15%
limitation.

(2) Pledge, mortgage or hypothecate in excess of 33 1/3% of its gross
assets. For purposes of this restriction, collateral arrangements with
respect to any type of swap, option, Futures Contracts and Forward
Contracts and payments of initial and variation margin in connection
therewith, are not considered a pledge of assets.

(3) Invest for the purpose of exercising control or management."

The date of this Supplement is November 1, 1999.

2
<PAGE>
PART C

Item 23. Financial Statements and Exhibits

(a) Financial Statements Included in Part A:

For the years or periods, as applicable to each operational series,
ended December 31, 1998*:

Financial Highlights

Financial Statements Included in Part B:

Portfolios of Investments, December 31, 1998* Statement of Assets and
Liabilities, December 31, 1998* Statements of Operations, year ended
December 31, 1998* Statements of Changes in Net Assets, years ended
December 31, 1997 and 1998.*
- -----------------------

* Incorporated herein by reference to the Registrant's Annual Reports to
shareholders, dated December 31, 1998, filed with the SEC via EDGAR on March
8, 1999.

(b) Exhibits:

1 (a) Amended and Restated Declaration of Trust of Registrant
dated December 29, 1997. (3)

(b) Amendment to the Declaration of Trust, to change the
name of certain series, dated April 29, 1999; filed
herewith.

2 By-Laws of Registrant dated February 6, 1998. (3)

3 Not Applicable.

4 (a) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company dated May 24,
1985. (3)
<PAGE>

(b) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company dated July 23,
1986. (3)

(c) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company dated January
26, 1988. (3)

(d) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating to
the World Growth Series dated November 1, 1993. (3)

(e) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating to
the Utilities Series dated November 1, 1993. (3)

(f) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating to
the Research Series dated September 16, 1994. (3)

(g) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating to
the World Asset Allocation Series dated September
16, 1994. (3)

(h) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating to
the World Total Return Series dated September 16,
1994. (3)

(i) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating to
the Emerging Growth Series dated May 1, 1995. (3)

(j) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating to
the MFS/Foreign & Colonial International Growth
Series dated September 1, 1995. (3)
<PAGE>

(k) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating to
the MFS/Foreign & Colonial International Growth and
Income Series dated September 1, 1995. (3)

(l) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating to
the MFS/Foreign & Colonial Emerging Markets Equity
Series dated September 1, 1995. (3)

(m) Sub-Advisory Agreement by and between Massachusetts
Financial Services Company and Foreign & Colonial
Management Ltd. relating to the MFS/Foreign &
Colonial International Growth Series dated
September 1, 1995. (3)

(n) Sub-Advisory Agreement by and between Massachusetts
Financial Services Company and Foreign & Colonial
Management Ltd. relating to the MFS/Foreign &
Colonial Emerging Markets Equity Series dated
September 1, 1995. (3)

(o) Sub-Advisory Agreement between Foreign & Colonial
Management Ltd. and Foreign & Colonial Emerging
Markets Limited relating to the MFS/Foreign & Colonial
International Growth Series dated September 1,
1995. (3)

(p) Sub-Advisory Agreement between Foreign & Colonial
Management Ltd. and Foreign & Colonial Emerging
Markets Limited relating to the MFS/Foreign & Colonial
Emerging Markets Equity Series dated September 1,
1995. (3)

(q) Sub-Advisory Agreement by and between Massachusetts
Financial Services Company and Foreign & Colonial
Management Limited relating to the World Growth
Series dated May 1, 1996. (3)
<PAGE>

(r) Sub-Advisory Agreement between Foreign & Colonial
Management Limited and Foreign & Colonial Emerging
Markets Limited relating to the World Growth Series
dated May 1, 1996. (3)

(s) Investment Advisory Agreement between Registrant and
Massachusetts Financial Services Company relating
to the Value Series dated May 1, 1996. (3)

(t) Investment Advisory Agreement between Registrant, on
behalf of the Research Growth and Income Series,
and Massachusetts Financial Services Company dated
May 12, 1997. (3)

(u) Amendment to the Investment Advisory Agreement by and
between Massachusetts Financial Services Company
and the Registrant relating to the Capital Appreciation
Series dated January 1, 1997. (1)

(v) Investment Advisory Agreement between Registrant, on
behalf of the Bond Series, and Massachusetts
Financial Services Company dated May 1, 1998. (5)

(w) Investment Advisory Agreement between Registrant, on
behalf of the Equity Income Series, and
Massachusetts Financial Services Company dated May 1,
1998. (5)

(x) Investment Advisory Agreement between Registrant, on
behalf of the Massachusetts Investors Growth Stock
Series, and Massachusetts Financial Services Company
dated May 1, 1998. (5)

(y) Investment Advisory Agreement between Registrant, on
behalf of the New Discovery Series, and
Massachusetts Financial Services Company dated May 1,
1998. (5)
<PAGE>

(z) Investment Advisory Agreement between Registrant, on
behalf of the Research International Series,
and Massachusetts Financial Services Company dated
May 1, 1998. (5)

(aa) Investment Advisory Agreement between Registrant, on
behalf of the Strategic Income Series, and
Massachusetts Financial Services Company dated May 1,
1998. (5)

(bb) Form of Investment Advisory Agreement between
Registrant, on behalf of the Strategic Growth Series,
and Massachusetts Financial Services Company;
filed herewith.

5 Not Applicable.

6 Not Applicable.

7 (a) Custodian Agreement between Registrant and State Street
Bank and Trust Company dated May 24, 1985. (3)

(b) Amendment dated July 23, 1986 to Custodian
Agreement. (3)

8 (a) Shareholder Servicing Agent Agreement between
Registrant and MFS Service Center, Inc., dated
August 1, 1985. (3)

(b) Master Administrative Services Agreement, dated March
1, 1997, as amended and restated April 1, 1999. (2)

9 (a) Consent and Opinion of Counsel dated April 24, 1998.(4)

(b) Consent of Counsel, dated August 11, 1999; filed
herewith.

10 Consent of Deloitte & Touche LLP. (5)

11 Not Applicable.
<PAGE>

12 Not Applicable.

13 Not Applicable.

14 Financial Data Schedules. (5)

15 Not Applicable.

Power of Attorney dated July 24, 1997. (4)

(1) Incorporated by reference to Post-Effective Amendment No. 20 to the
Registrant's Registration Statement filed via EDGAR on April 29, 1997.

(2) Incorporated by reference to MFS Series Trust III (File Nos. 2-60491 and
811-2794) Post-Effective Amendment No. 28 filed via EDGAR on March 31,
1999.

(3) Incorporated by reference to Post-Effective Amendment No. 21 to the
Registrant's Registration Statement filed via EDGAR on February 13, 1998.
(4) Incorporated by reference to Post-Effective Amendment No. 22 to the
Registrant's Registration Statement filed via EDGAR on April 29, 1998.

(5) Incorporated by reference to Post-Effective Amendment No. 23 to the
Registrant's Registration Statement filed via EDGAR on February 22, 1999.

Item 24. Persons Controlled by or under Common Control with Registrant

Not applicable.

Item 25. Indemnification

Reference is hereby made to (a) Article V of the Registrant's
Amended and Restated Declaration of Trust, filed as an Exhibit to the
Registrant's Post-Effective Amendment No. 21 and (b) the undertaking of the
Registrant regarding indemnification set forth in Registrant's Post-Effective
Amendment No. 21.

The Trustees and officers of the Registrant and the personnel
of the Registrant's investment adviser are insured under an errors and omissions
liability insurance policy. The Registrant and its officers are also insured
under the fidelity bond required by Rule 17g-1 under the Investment Company Act
of 1940.

Item 26. Business and Other Connections of Investment Adviser

MFS serves as investment adviser to the following open-end
Funds comprising the MFS Family of Funds (except the Vertex Funds mentioned
below): Massachusetts Investors Trust, Massachusetts Investors Growth Stock
Fund, MFS Growth Opportunities Fund, MFS Government Securities Fund, MFS
Government Limited Maturity Fund, MFS Series Trust I (which has twelve series:
MFS Managed Sectors Fund, MFS Cash

<PAGE>

Reserve Fund, MFS Global Asset Allocation Fund, MFS Strategic Growth Fund, MFS
Research Growth and Income Fund, MFS Core Growth Fund, MFS Equity Income Fund,
MFS Convertible Securities Fund, MFS Blue Chip Fund, MFS New Discovery Fund, MFS
Science and Technology Fund and MFS Research International Fund), MFS Series
Trust II (which has four series: MFS Emerging Growth Fund, MFS Large Cap Growth
Fund, MFS Intermediate Income Fund and MFS Charter Income Fund), MFS Series
Trust III (which has three series: MFS High Income Fund, MFS Municipal High
Income Fund and MFS High Yield Opportunities Fund), MFS Series Trust IV (which
has four series: MFS Money Market Fund, MFS Government Money Market Fund, MFS
Municipal Bond Fund and MFS Mid Cap Growth Fund), MFS Series Trust V (which has
five series: MFS Total Return Fund, MFS Research Fund, MFS International
Opportunities Fund, MFS International Strategic Growth Fund and MFS
International Value Fund), MFS Series Trust VI (which has three series: MFS
Global Total Return Fund, MFS Utilities Fund and MFS Global Equity Fund), MFS
Series Trust VII (which has two series: MFS Global Governments Fund and MFS
Capital Opportunities Fund), MFS Series Trust VIII (which has two series: MFS
Strategic Income Fund and MFS Global Growth Fund), MFS Series Trust IX (which
has eight series: MFS Bond Fund, MFS Limited Maturity Fund, MFS Municipal
Limited Maturity Fund, MFS Research Bond Fund, MFS Intermediate Investment Grade
Bond Fund, MFS Mid Cap Value Fund, MFS Large Cap Value Fund and MFS High Quality
Bond Fund), MFS Series Trust X (which has seven series: MFS Government Mortgage
Fund, MFS/Foreign & Colonial Emerging Markets Equity Fund, MFS International
Growth Fund, MFS International Growth and Income Fund, MFS Strategic Value Fund,
MFS Small Cap Value Fund and MFS Emerging Markets Debt Fund), MFS Series Trust
XI (which has four series: MFS Union Standard Equity Fund, Vertex All Cap Fund,
Vertex U.S. All Cap Fund and Vertex Contrarian Fund), and MFS Municipal Series
Trust (which has 16 series: MFS Alabama Municipal Bond Fund, MFS Arkansas
Municipal Bond Fund, MFS California Municipal Bond Fund, MFS Florida Municipal
Bond Fund, MFS Georgia Municipal Bond Fund, MFS Maryland Municipal Bond Fund,
MFS Massachusetts Municipal Bond Fund, MFS Mississippi Municipal Bond Fund, MFS
New York Municipal Bond Fund, MFS North Carolina Municipal Bond Fund, MFS
Pennsylvania Municipal Bond Fund, MFS South Carolina Municipal Bond Fund, MFS
Tennessee Municipal Bond Fund, MFS Virginia Municipal Bond Fund, MFS West
Virginia Municipal Bond Fund and MFS Municipal Income Fund) (the "MFS Funds").
The principal business address of each of the MFS Funds is 500 Boylston Street,
Boston, Massachusetts 02116.

MFS also serves as investment adviser of the following open-end Funds:
MFS Institutional Trust ("MFSIT") (which has ten series) and MFS Variable
Insurance Trust ("MVI") (which has fifteen series). The principal business
address of each of the aforementioned funds is 500 Boylston Street, Boston,
Massachusetts 02116.

In addition, MFS serves as investment adviser to the following
closed-end funds: MFS Municipal Income Trust, MFS Multimarket Income Trust, MFS
Government Markets Income Trust, MFS Intermediate Income Trust, MFS Charter
Income Trust and

<PAGE>

MFS Special Value Trust (the "MFS Closed-End Funds"). The principal business
address of each of the MFS Closed-End Funds is 500 Boylston Street, Boston,
Massachusetts 02116.

Lastly, MFS serves as investment adviser to MFS/Sun Life Series
Trust ("MFS/SL") (which has 26 series), Money Market Variable Account, High
Yield Variable Account, Capital Appreciation Variable Account, Government
Securities Variable Account, Global Governments Variable Account, Total Return
Variable Account and Managed Sectors Variable Account (collectively, the
"Accounts"). The principal business address of MFS/SL is 500 Boylston Street,
Boston, Massachusetts 02116. The principal business address of each of the
aforementioned Accounts is One Sun Life Executive Park, Wellesley Hills,
Massachusetts 02181.

Vertex Investment Management, Inc., a Delaware corporation and a
wholly owned subsidiary of MFS, whose principal business address is 500 Boylston
Street, Boston, Massachusetts 02116 ("Vertex"), serves as investment adviser to
Vertex All Cap Fund, Vertex U.S. All Cap Fund and Vertex Contrarian Fund, each a
series of MFS Series Trust XI. The principal business address of the
aforementioned Funds is 500 Boylston Street, Boston, Massachusetts 02116.

MFS International Ltd. ("MIL"), a limited liability company
organized under the laws of Bermuda and a subsidiary of MFS, whose principal
business address is Cedar House, 41 Cedar Avenue, Hamilton HM12 Bermuda, serves
as investment adviser to and distributor for MFS American Funds known as the MFS
Funds after January 1999 (which will have 11 portfolios as of January 1999):
U.S. Equity Fund, U.S. Emerging Growth Fund, U.S. High Yield Bond Fund, U.S.
Dollar Reserve Fund, Charter Income Fund, U.S. Research Fund, U.S. Strategic
Growth Fund, Global Equity Fund, European Equity Fund and European Corporate
Bond Fund) (the "MIL Funds"). The MIL Funds are organized in Luxembourg and
qualify as an undertaking for collective investments in transferable securities
(UCITS). The principal business address of the MIL Funds is 47, Boulevard Royal,
L-2449 Luxembourg. MIL also serves as investment adviser to and distributor for
MFS Meridian U.S. Government Bond Fund, MFS Meridian Charter Income Fund, MFS
Meridian Global Governments Fund, MFS Meridian U.S. Emerging Growth Fund, MFS
Meridian Global Equity Fund, MFS Meridian Limited Maturity Fund, MFS Meridian
Global Growth Fund, MFS Meridian Money Market Fund, MFS Meridian Global Balanced
Fund, MFS Meridian U.S. Equity Fund, MFS Meridian Research Fund, MFS Meridian
U.S. High Yield Fund, MFS Meridian Emerging Markets Debt Fund, MFS Meridian
Strategic Growth Fund and MFS Meridian Global Asset Allocation Fund and the MFS
Meridian Research International Fund (collectively the "MFS Meridian Funds").
Each of the MFS Meridian Funds is organized as an exempt company under the laws
of the Cayman Islands. The principal business address of each of the MFS
Meridian Funds is P.O. Box 309, Grand Cayman, Cayman Islands, British West
Indies.

<PAGE>

MFS International (U.K.) Ltd. ("MIL-UK"), a private limited company
registered with the Registrar of Companies for England and Wales whose current
address is Eversheds, Senator House, 85 Queen Victoria Street, London, England
EC4V 4JL, is involved primarily in marketing and investment research activities
with respect to private clients and the MIL Funds and the MFS Meridian Funds.

MFS Institutional Advisors (Australia) Ltd. ("MFSI-Australia"), a
private limited company organized under the Corporations Law of New South Wales,
Australia whose current address is Level 27, Australia Square, 264 George
Street, Sydney, NSW2000, Australia, is involved primarily in investment
management and distribution of Australian superannuation unit trusts and acts as
an investment adviser to institutional accounts.

MFS Holdings Australia Pty Ltd. ("MFS Holdings Australia"), a
private limited company organized pursuant to the Corporations Law of New South
Wales, Australia whose current address is Level 27, Australia Square, 264 George
Street, Sydney, NSW2000 Australia, and whose function is to serve primarily as a
holding company.

MFS Fund Distributors, Inc. ("MFD"), a wholly owned subsidiary of MFS,
serves as distributor for the MFS Funds, MVI and MFSIT.

MFS Service Center, Inc. ("MFSC"), a wholly owned subsidiary of MFS,
serves as shareholder servicing agent to the MFS Funds, the MFS Closed-End
Funds, MFSIT and MVI.

MFS Institutional Advisors, Inc. ("MFSI"), a wholly owned subsidiary
of MFS, provides investment advice to substantial private clients.

MFS Retirement Services, Inc. ("RSI"), a wholly owned subsidiary of
MFS, markets MFS products to retirement plans and provides administrative and
record keeping services for retirement plans.

Massachusetts Investment Management Co., Ltd. ("MIMCO"), a wholly
owned subsidiary of MFS, is a corporation incorporated in Japan. MIMCO, whose
address is Kamiyacho-Mori Building, 3-20, Tranomon 4-chome, Minato-ku, Tokyo,
Japan, is involved in investment management activities.

MFS Heritage Trust Company ("MFS Trust"), a New Hampshire-chartered
limited-purpose trust company whose current address is 650 Elm Street, Suite
404, Manchester, NH 03101, provides directed trustee services to retirement
plans.

<PAGE>

United Funds Management LTD. ("UFM"), an Australian Company organized
under the Corporations Law of New South Wales, Australia whose current address
is Level 27, Australia Square 264-278, George St., Sydney, NSW2000, is an
investment manager and distributor of Australian superannuation unit trusts.

MFS

The Directors of MFS are Jeffrey L. Shames, Arnold D. Scott, John W.
Ballen, Kevin R. Parke, Thomas J. Cashman, Jr., Joseph W. Dello Russo, William
W. Scott, Donald A. Stewart and John D. McNeil. Mr. Shames is the Chairman and
Chief Executive Officer, Mr. Ballen is President and Chief Investment Officer,
Mr. Arnold Scott is a Senior Executive Vice President and Secretary, Mr. William
Scott, Mr. Cashman, Mr. Dello Russo and Mr. Parke are Executive Vice Presidents
(Mr. Joseph W. Dello Russo is also Chief Financial Officer and Chief
Administrative Officer), (Mr. Parke is also Chief Equity Officer), Stephen E.
Cavan is a Senior Vice President, General Counsel and an Assistant Secretary,
Robert T. Burns is a Senior Vice President, Associate General Counsel and an
Assistant Secretary of MFS, and Thomas B. Hastings is a Vice President and
Treasurer of MFS.

Massachusetts Investors Trust
Massachusetts Investors Growth Stock Fund
MFS Growth Opportunities Fund
MFS Government Securities Fund
MFS Series Trust I
MFS Series Trust V
MFS Series Trust VI
MFS Series Trust X
MFS Government Limited Maturity Fund

Stephen E. Cavan is the Secretary, W. Thomas London is the Treasurer,
James O. Yost, Ellen M. Moynihan and Mark E. Bradley, Vice Presidents of MFS,
are the Assistant Treasurers, James R. Bordewick, Jr., Senior Vice President and
Associate General Counsel of MFS, is the Assistant Secretary.

MFS Series Trust II

Leslie J. Nanberg, Senior Vice President of MFS, is a Vice President,
Stephen E. Cavan is the Secretary, W. Thomas London is the Treasurer, James O.
Yost, Ellen M. Moynihan and Mark E. Bradley are the Assistant Treasurers, and
James R. Bordewick, Jr. is the Assistant Secretary.

<PAGE>

MFS Government Markets Income Trust
MFS Intermediate Income Trust

MFS Series Trust III

James T. Swanson, Robert J. Manning and Joan S. Batchelder, Senior
Vice Presidents of MFS, and Bernard Scozzafava, Vice President of MFS, are Vice
Presidents, Stephen E. Cavan is the Secretary, W. Thomas London is the
Treasurer, James O. Yost, Ellen M. Moynihan and Mark E. Bradley are the
Assistant Treasurers, and James R. Bordewick, Jr. is the Assistant Secretary.

MFS Series Trust IV
MFS Series Trust IX

Robert A. Dennis and Geoffrey L. Kurinsky, Senior Vice Presidents of
MFS, are Vice Presidents, Stephen E. Cavan is the Secretary, W. Thomas London is
the Treasurer, James O. Yost, Ellen M. Moynihan and Mark E. Bradley are the
Assistant Treasurers and James R. Bordewick, Jr. is the Assistant Secretary.

MFS Series Trust VII

Leslie J. Nanberg and Stephen C. Bryant, Senior Vice Presidents of
MFS, are Vice Presidents, Stephen E. Cavan is the Secretary, W. Thomas London is
the Treasurer, James O. Yost, Ellen M. Moynihan and Mark E. Bradley are the
Assistant Treasurers and James R. Bordewick, Jr. is the Assistant Secretary.

MFS Series Trust VIII

Jeffrey L. Shames, Leslie J. Nanberg and James T. Swanson and John D.
Laupheimer, Jr., a Senior Vice President of MFS, are Vice Presidents, Stephen E.
Cavan is the Secretary, W. Thomas London is the Treasurer, James O. Yost, Ellen
M. Moynihan and Mark E. Bradley are the Assistant Treasurers and James R.
Bordewick, Jr. is the Assistant Secretary.

MFS Municipal Series Trust

Robert A. Dennis is Vice President, Geoffrey L. Schechter, Vice
President of MFS, is Vice President, Stephen E. Cavan is the Secretary, W.
Thomas London is the

<PAGE>

Treasurer, James O. Yost, Ellen M. Moynihan and Mark E. Bradley are the
Assistant Treasurers and James R. Bordewick, Jr. is the Assistant Secretary.

MFS Variable Insurance Trust
MFS Series Trust XI
MFS Institutional Trust

Jeffrey L. Shames is the President and Chairman, Stephen E. Cavan is
the Secretary, W. Thomas London is the Treasurer, James O. Yost, Ellen M.
Moynihan and Mark E. Bradley are the Assistant Treasurers and James R.
Bordewick, Jr. is the Assistant Secretary.

MFS Municipal Income Trust

Robert J. Manning is Vice President, Stephen E. Cavan is the
Secretary, W. Thomas London is the Treasurer, James O. Yost, Ellen M. Moynihan
and Mark E. Bradley are the Assistant Treasurers and James R. Bordewick, Jr. is
the Assistant Secretary.

MFS Multimarket Income Trust
MFS Charter Income Trust

Leslie J. Nanberg and James T. Swanson are Vice Presidents, Stephen E.
Cavan is the Secretary, W. Thomas London is the Treasurer, James O. Yost, Ellen
M. Moynihan and Mark E. Bradley are the Assistant Treasurers and James R.
Bordewick, Jr. is the Assistant Secretary.

MFS Special Value Trust

MFS/Sun Life Series Trust

John D. McNeil, Chairman and Director of Sun Life Assurance Company of
Canada, is the Chairman, Stephen E. Cavan is the Secretary, W. Thomas London is
the Treasurer, James O. Yost, Ellen M. Moynihan and Mark E. Bradley are the
Assistant Treasurers and James R. Bordewick, Jr. is the Assistant Secretary.

<PAGE>

Money Market Variable Account
High Yield Variable Account
Capital Appreciation Variable Account
Government Securities Variable Account
Total Return Variable Account
World Governments Variable Account
Managed Sectors Variable Account

John D. McNeil is the Chairman, Stephen E. Cavan is the Secretary, and
James R. Bordewick, Jr. is the Assistant Secretary.

MIL Funds

Richard B. Bailey, John A. Brindle, Richard W. S. Baker, Arnold D.
Scott, Jeffrey L. Shames and William F. Waters are Directors, Stephen E. Cavan
is the Secretary, W. Thomas London is the Treasurer, James O. Yost, Ellen M.
Moynihan and Mark E. Bradley are the Assistant Treasurers and James R.
Bordewick, Jr. is the Assistant Secretary.

MFS Meridian Funds

Richard B. Bailey, John A. Brindle, Richard W. S. Baker, Arnold D.
Scott, Jeffrey L. Shames and William F. Waters are Directors, Stephen E. Cavan
is the Secretary, W. Thomas London is the Treasurer, James R. Bordewick, Jr. is
the Assistant Secretary and James O. Yost, Ellen M. Moynihan and Mark E. Bradley
are the Assistant Treasurers.

Vertex

Jeffrey L. Shames and Arnold D. Scott are the Directors, Jeffrey L.
Shames is the President, Kevin R. Parke and John W. Ballen are Executive Vice
Presidents, John D. Laupheimer is a Senior Vice President, Brian E. Stack is a
Vice President, Joseph W. Dello Russo is the Treasurer, Thomas B. Hastings is
the Assistant Treasurer, Stephen E. Cavan is the Secretary and Robert T. Burns
is the Assistant Secretary.

MIL

Peter D. Laird is President and a Director, Arnold D. Scott, Jeffrey
L. Shames and Thomas J. Cashman, Jr. are Directors, Stephen E. Cavan is a
Director, Senior Vice President and the Clerk, Robert T. Burns is an Assistant
Clerk, Joseph W. Dello Russo, Executive Vice President and Chief Financial
Officer of MFS, is the Treasurer and Thomas B. Hastings is the Assistant
Treasurer.

<PAGE>

MIL-UK

Peter D. Laird is President and a Director, Thomas J. Cashman, Arnold
D. Scott and Jeffrey L. Shames are Directors, Stephen E. Cavan is a Director and
the Secretary, Joseph W. Dello Russo is the Treasurer, Thomas B. Hastings is the
Assistant Treasurer and Robert T. Burns is the Assistant Secretary.

MFSI - Australia

Thomas J. Cashman, Jr. is President and a Director, Graham E. Lenzer,
John A. Gee and David Adiseshan are Directors, Stephen E. Cavan is the
Secretary, Joseph W. Dello Russo is the Treasurer, Thomas B. Hastings is the
Assistant Treasurer, and Robert T. Burns is the Assistant Secretary.

MFS Holdings - Australia

Jeffrey L. Shames is the President and a Director, Arnold D. Scott,
Thomas J. Cashman, Jr., and Graham E. Lenzer are Directors, Stephen E. Cavan is
the Secretary, Joseph W. Dello Russo is the Treasurer, Thomas B. Hastings is the
Assistant Treasurer, and Robert T. Burns is the Assistant Secretary.

MFD

Arnold D. Scott and Jeffrey L. Shames are Directors, William W. Scott,
Jr., an Executive Vice President of MFS, is the President, Stephen E. Cavan is
the Secretary, Robert T. Burns is the Assistant Secretary, Joseph W. Dello Russo
is the Treasurer, and Thomas B. Hastings is the Assistant Treasurer.

MFSC

Arnold D. Scott and Jeffrey L. Shames are Directors, Joseph A.
Recomendes, a Senior Vice President and Chief Information Officer of MFS, is
Vice Chairman and a Director, Janet A. Clifford is the President, Joseph W.
Dello Russo is the Treasurer, Thomas B. Hastings is the Assistant Treasurer,
Stephen E. Cavan is the Secretary, and Robert T. Burns is the Assistant
Secretary.

MFSI

Thomas J. Cashman, Jr. is Chairman and a Director, Jeffrey L. Shames,
and Arnold D. Scott are Directors, Joseph J. Trainor is the President and a
Director, Leslie J. Nanberg is a Senior Vice President, a Managing Director and
a Director, Kevin R. Parke is the Executive Vice President and a Managing
Director, George F. Bennett, Jr., John A. Gee, Brianne Grady, Joseph A.
Kosciuszek and Joseph J. Trainor are Senior Vice

<PAGE>

Presidents and Managing Directors, Joseph W. Dello Russo is the Treasurer,
Thomas B. Hastings is the Assistant Treasurer and Robert T. Burns is the
Secretary.

RSI

Arnold D. Scott is the Chairman and a Director, Martin E. Beaulieu is
the President, William W. Scott, Jr. is a Director, Joseph W. Dello Russo is the
Treasurer, Thomas B. Hastings is the Assistant Treasurer, Stephen E. Cavan is
the Secretary and Robert T. Burns is the Assistant Secretary.

MIMCO

Jeffrey L. Shames, Arnold D. Scott and Mamoru Ogata are Directors,
Shaun Moran is the Representative Director, Joseph W. Dello Russo is the
Statutory Auditor, Robert DiBella is the President and Thomas B. Hastings is the
Assistant Statutory Auditor.

MFS Trust

The Directors of MFS Trust are Martin E. Beaulieu, Stephen E. Cavan,
Janet A. Clifford, Joseph W. Dello Russo and Joseph A. Kosciuszek. Mr. Cavan is
President, Mr. Dello Russo is Treasurer, and Robert T. Burns is Clerk of MFS
Trust.

UFM

The Directors of UFM are Thomas J. Cashman, Jr. and Susan Gosling.
Graham Lenzner is the Chairman and Thomas J. Murray is Chief Financial Officer,
Treasurer and Secretary.

In addition, the following persons, Directors or officers of MFS, have
the affiliations indicated:

Donald A. Stewart President and a Director, Sun Life
Assurance Company of Canada, Sun
Life Centre, 150 King Street West,
Toronto, Ontario, Canada (Mr.
Stewart is also an officer and/or
Director of various subsidiaries
and affiliates of Sun Life)

John D. McNeil Chairman, Sun Life Assurance
Company of Canada, Sun Life Centre,
150 King Street West, Toronto,
Ontario, Canada (Mr. McNeil

<PAGE>

is also an officer and/or Director
of various subsidiaries and
affiliates of Sun Life)

Joseph W. Dello Russo Director of Mutual Fund Operations,
The Boston Company, Exchange Place,
Boston, Massachusetts (until
August, 1994)

Item 27. Distributors

None

Item 28. Location of Accounts and Records

The accounts and records of the Registrant are located, in whole or in
part, at the office of the Registrant and the following locations:

NAME ADDRESS

Massachusetts Financial Services 500 Boylston Street
Company (investment adviser) Boston, MA 02116

MFS Service Center, Inc. 2 Avenue de Lafayette
Boston, MA 02111

State Street Bank and Trust Company State Street South
5-North
North Quincy, MA 02171

Sun Life Assurance Company of Canada One Copley Place
Retirement Products and Services Suite 200
Boston, MA 02116

Item 29. Management Services

Not applicable.

Item 30. Undertakings

Not applicable.
<PAGE>

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the
Investment Company Act of 1940, the Registrant has duly caused this
Post-Effective Amendment to the Registration Statement to be signed on its
behalf by the undersigned, thereto duly authorized, in the City of Boston and
The Commonwealth of Massachusetts on the 11th day of August, 1999.

MFS/SUN LIFE SERIES TRUST

By: JAMES R. BORDEWICK, JR.
Name: James R. Bordewick, Jr.
Title: Assistant Secretary

Pursuant to the requirements of the Securities Act of 1933, this
Post-Effective Amendment to its Registration Statement has been signed below by
the following persons in the capacities indicated on August 11, 1999.

SIGNATURE TITLE

JOHN D. MCNEIL* Chairman, Principal Executive
John D. McNeil Officer and Trustee

W. THOMAS LONDON* Treasurer (Principal Financial Officer
W. Thomas London and Principal Accounting Officer)

SAMUEL ADAMS* Trustee
Samuel Adams

GEOFFREY CROFTS* Trustee
Geoffrey Crofts

GARTH MARSTON* Trustee
Garth Marston

<PAGE>

DAVID D. HORN* Trustee
David D. Horn

DERWYN F. PHILLIPS* Trustee
Derwyn F. Phillips

*By: JAMES R. BORDEWICK, JR.
Name: James R. Bordewick, Jr.
as Attorney-in-fact

Executed by James R. Bordewick, Jr. on
behalf of those indicated pursuant to a
Power of Attorney filed via EDGAR with
Post-Effective Amendment No. 22 to the
Registrant's Registration Statement on
April 29, 1998.

<PAGE>

INDEX TO EXHIBITS

EXHIBIT NO. DESCRIPTION OF EXHIBIT PAGE NO.

1 (b) Amendment to the Declaration of Trust, to
change the name of certain series,
dated April 29, 1999.

4 (bb) Form of Investment Advisory Agreement
between Registrant, on behalf of
the Strategic Growth Series, and
Massachusetts Financial Services
Company.

9 (b) Consent of Counsel, dated August 11, 1999.

<PAGE>
EXHIBIT NO. 99.1(b)

MFS/SUN LIFE SERIES TRUST

AMENDMENT to the DECLARATION OF TRUST

CERTIFICATION OF AMENDMENT
TO THE DECLARATION OF TRUST

REDESIGNATION OF SERIES

The undersigned, being a majority of the Trustees of MFS/Sun Life
Series Trust (the "Trust"), a business trust organized under the laws of The
Commonwealth of Massachusetts pursuant to an Amended and Restated Declaration of
Trust dated December 29, 1997, as amended (the "Declaration"), acting pursuant
to Section 6.9 of the Declaration, do hereby redesignate an existing series of
Shares (as defined in the Declaration) as follows:

1. The series designated as Conservative Growth Series shall be
redesignated as Massachusetts Investors Trust Series;

2. The series designated as World Asset Allocation Series shall be
redesignated as Global Asset Allocation Series;

3. The series designated as World Governments Series shall be
redesignated as Global Governments Series;

4. The series designated as World Growth Series shall be
redesignated as Global Growth Series; and

5. The series designated as World Total Return Series shall be
redesignated as Global Total Return Series.

<PAGE>

Pursuant to Section 6.9(h) of the Declaration, this redesignation of
series of Shares shall be effective upon the execution of a majority of the
Trustees of the Trust.

IN WITNESS WHEREOF, a majority of the Trustees of the Trust have
executed this establishment and designation, in one or more counterparts, all
constituting a single instrument, as an instrument under seal in The
Commonwealth of Massachusetts, as of this 29th day of April, 1999.

SAMUEL ADAMS J. KERMIT BIRCHFIELD
Samuel Adams J. Kermit Birchfield
11 University Lane 33 Way Road
Manchester, MA 01944 Gloucester, MA 01930

WILLIAM R. GUTOW DAVID D. HORN
William R. Gutow David D. Horn
3 Rue Dulac Strong Road
Dallas, TX 75230 New Vineyard, ME 04956

GARTH MARSTON JOHN D. MCNEIL
Garth Marston John D. McNeil
90 Beacon Street 10 McKenzie Avenue
Boston, MA 02108 Toronto, Ontario
Canada M4W 1J9

DERWYN F. PHILLIPS
Derwyn F. Phillips
1250 West Southwinds Blvd.
Vero Beach, FL 32963
<PAGE>

<PAGE>
EXHIBIT NO. 99.1(c)

MFS/SUN LIFE SERIES TRUST

FORM OF

CERTIFICATION OF AMENDMENT
TO THE DECLARATION OF TRUST

ESTABLISHMENT AND DESIGNATION
OF SERIES

Pursuant to Section 6.9 of the Amended and Restated Declaration of
Trust dated December 29, 1997, as amended (the "Declaration") of MFS/Sun Life
Series Trust, a business Trust organized under the laws of The Commonwealth of
Massachusetts (the "Trust"), the undersigned Trustees of the Trust, being a
majority of the Trustees of the Trust, hereby establish and designate a new
series of Shares (as defined in the Declaration), such series to have the
following special and relative rights:

1. The new series shall be designated:

- Strategic Growth Series

2. The series shall be authorized to invest in cash, securities,
instruments and other property as from time to time described in
the Trust's then currently effective registration statement under
the Securities Act of 1933, as amended, to the extent pertaining
to the offering of Shares of such series. Each Share of the
series shall be redeemable, shall be entitled to one vote or
fraction thereof in respect of a fractional share on matters on
which Shares of the series shall be entitled to vote, shall
represent a pro rata beneficial interest in the assets allocated
or belonging to the series, and shall be entitled to receive its
pro rata share of the net assets of the series upon liquidation
of the series, all as provided in Section 6.9 of the Declaration.

3. Shareholders of the series shall vote separately as a class from
shareholders of each other series on any matter to the extent
required by, and any matter shall be deemed to have been
effectively acted upon with respect to the series as provided in
Rule 18f-2, as from time to time in effect, under the Investment
Company
<PAGE>

Act of 1940, as amended, or any successor rule, and by the
Declaration.

4. The assets and liabilities of the Trust shall be allocated among
the previously established and existing series of the Trust and
such new series as set forth in Section 6.9 of the Declaration.

5. Subject to the provisions of Section 6.9 and Article IX of the
Declaration, the Trustees (including any successor Trustees)
shall have the right at any time and from time to time to
reallocate assets and expenses or to change the designation of
any series now or hereafter created, or to otherwise change the
special and relative rights of any such establishment and
designation of series of Shares.

Pursuant to Section 6.9 of the Declaration, this establishment and
designation of series of Shares shall be effective upon the execution by a
majority of the Trustees of the Trust.
<PAGE>

IN WITNESS WHEREOF, a majority of the Trustees of the Trust have
executed this amendment, in one or more counterparts, all constituting a single
instrument, as an instrument under seal in The Commonwealth of Massachusetts, as
of this ______ day of ___________________, 1999 and further certify, as
provided by the provisions of Section 9.3(d) of The Declaration, that this
amendment was duly adopted by the undersigned in accordance with the second
sentence of Section 9.3(a) of the Declaration.

- ---------------------- ---------------------
Samuel Adams Garth Marston
23 University Lane 90 Beacon Street
Manchester, MA 01944 Boston, MA 02108

- ---------------------- ---------------------
J. Kermit Birchfield John D. McNeil
33 Way Road 10 McKenzie Avenue
Gloucester, MA 01930 Toronto, Ontario
Canada M4W 1J9

- ----------------------- ---------------------
William R. Gutow Derwyn F. Phillips
3 Rue Dulac 22 Cliff Street
Dallas, TX 75230 Marblehead, MA 01945

- -----------------------
David D. Horn
Strong Road
New Vineyard, ME 04956

<PAGE>

EXHIBIT NO. 99.4(bb)

FORM OF

INVESTMENT ADVISORY AGREEMENT

INVESTMENT ADVISORY AGREEMENT, dated this 1st day of November, 1999, by and
between MFS/SUN LIFE SERIES TRUST, a Massachusetts business trust (the "Trust"),
on behalf of STRATEGIC GROWTH SERIES, a series of the Trust (the "Fund"), and
MASSACHUSETTS FINANCIAL SERVICES COMPANY, a Delaware corporation (the
"Adviser").

WITNESSETH:

WHEREAS, the Trust is engaged in business as an open-end investment company
registered under the Investment Company Act of 1940; and

WHEREAS, the Adviser is willing to provide business services to the Fund on
the terms and conditions hereinafter set forth;

NOW, THEREFORE, in consideration of the mutual covenants and agreements of
the parties hereto as herein set forth, the parties covenant and agree as
follows:

Article 1. Duties of the Adviser. The Adviser shall provide the Fund with
such investment advice and supervision as the latter may from time to time
consider necessary for the proper supervision of its funds. The Adviser shall
act as Adviser to the Fund and as such shall furnish continuously an investment
program and shall determine from time to time what securities shall be
purchased, sold or exchanged and what portion of the assets of the Fund shall be
held uninvested, subject always to the restrictions of the Trust's Amended and
Restated Declaration of Trust, dated December 29, 1997, and By-Laws, each as
amended from time to time (respectively, the "Declaration" and the "By-Laws"),
to the provisions of the Investment Company Act of 1940 and the Rules,
Regulations and orders thereunder and to the Fund's then-current Prospectus and
Statement of Additional Information. The Adviser shall also make recommendations
as to the manner in which voting rights, rights to consent to corporate action
and any other rights pertaining to the Fund's portfolio securities shall be
exercised. Should the Trustees at any time, however, make any definite
determination as to the investment policy and notify the Adviser thereof in
writing, the Adviser shall be bound by such determination for the period, if
any, specified in such notice or until similarly notified that such
determination shall be revoked. The

1
<PAGE>

Adviser shall take, on behalf of the Fund, all actions which it deems necessary
to implement the investment policies determined as provided above, and in
particular to place all orders for the purchase or sale of portfolio securities
for the Fund's account with brokers or dealers selected by it, and to that end,
the Adviser is authorized as the agent of the Fund to give instructions to the
Custodian of the Fund as to the deliveries of securities and payments of cash
for the account of the Fund. In connection with the selection of such brokers or
dealers and the placing of such orders, the Adviser is directed to seek for the
Fund execution at the most reasonable price by responsible brokerage firms at
reasonably competitive commission rates. In fulfilling this requirement, the
Adviser shall not be deemed to have acted unlawfully or to have breached any
duty, created by this Agreement or otherwise, solely by reason of its having
caused the Fund to pay a broker or dealer an amount of commission for effecting
a securities transaction in excess of the amount of commission another broker or
dealer would have charged for effecting that transaction, if the Adviser
determined in good faith that such amount of commission was reasonable in
relation to the value of the brokerage and research services provided by such
broker or dealer, viewed in terms of either that particular transaction or the
Adviser's overall responsibilities with respect to the Fund and to other clients
of the Adviser as to which the Adviser exercises investment discretion.

The Adviser may from time to time enter into sub-investment advisory agreements
with one or more investment advisers with such terms and conditions as the
Adviser may determine, provided that such sub-investment advisory agreements
have been approved in accordance with applicable provisions of the Investment
Company Act of 1940. Subject to the provisions of Article 6, the Adviser shall
not be liable for any error of judgment or mistake of law by any sub-adviser or
for any loss arising out of any investment made by any sub-adviser or for any
act or omission in the execution and management of the Fund by any sub-adviser.

Article 2. Allocation of Charges and Expenses. The Adviser shall furnish at
its own expense investment advisory and administrative services, office space,
equipment and clerical personnel necessary for servicing the investments of the
Fund and maintaining its organization and investment advisory facilities and
executive and supervisory personnel for managing the investments and effecting
the portfolio transactions of the Fund. The Adviser shall arrange, if desired by
the Trust, for Directors, officers and employees of the Adviser to serve as
Trustees, officers or agents of the Trust if duly elected or appointed to such
positions and subject to their individual consent and to any limitations imposed
by law. It is understood that the Fund will pay all of its own expenses
including, without limitation, compensation of Trustees "not affiliated" with
the Adviser; governmental fees; interest charges; taxes; membership dues in the
Investment Company Institute allocable to the Fund; fees and expenses of
independent auditors, of legal counsel, and of any transfer agent, registrar or
dividend disbursing agent of the Fund; expenses of repurchasing and

2
<PAGE>

redeeming shares and servicing shareholder accounts; expenses of preparing,
printing and mailing stock certificates, shareholder reports, notices, proxy
statements and reports to governmental officers and commissions; brokerage and
other expenses connected with the execution, recording and settlement of
portfolio security transactions; insurance premiums; fees and expenses of the
custodian for all services to the Fund, including safekeeping of funds and
securities and maintaining required books and accounts; expenses of calculating
the net asset value of shares of the Fund; expenses of shareholders' meetings;
and expenses relating to the issuance, registration and qualification of shares
of the Fund and the preparation, printing and mailing of prospectuses for such
purposes (except to the extent that any Distribution Agreement to which the
Trust is a party provides that another party is to pay some or all of such
expenses).

Article 3. Compensation of the Adviser. For the services to be rendered and
the facilities provided, the Fund shall pay to the Adviser an investment
advisory fee computed and paid annually at a rate equal 0.75% of the Fund's
average daily net assets. If the Adviser shall serve for less than the whole of
any period specified in this Article 3, the compensation to the Adviser will be
prorated.

Article 4. Special Services. Should the Trust have occasion to request the
Adviser to perform services not herein contemplated or to request the Adviser to
arrange for the services of others, the Adviser will act for the Trust on behalf
of the Fund upon request to the best of its ability, with compensation for the
Adviser's services to be agreed upon with respect to each such occasion as it
arises.

Article 5. Covenants of the Adviser. The Adviser agrees that it will not
deal with itself, or with the Trustees of the Trust or the Trust's distributor,
if any, as principals in making purchases or sales of securities or other
property for the account of the Fund, except as permitted by the Investment
Company Act of 1940 and the Rules, Regulations or orders thereunder, will not
take a long or short position in the shares of the Fund except as permitted by
the Declaration, and will comply with all other provisions of the Declaration
and the By-Laws and the then-current Prospectus and Statement of Additional
Information of the Fund relative to the Adviser and its Directors and officers.

Article 6. Limitation of Liability of the Adviser. The Adviser shall not be
liable for any error of judgment or mistake of law or for any loss arising out
of any investment or for any act or omission in the execution and management of
the Fund, except for willful misfeasance, bad faith or gross negligence in the
performance of its duties and obligations hereunder. As used in this Article 6,
the term "Adviser" shall include Directors, officers and employees of the
Adviser as well as that corporation itself.

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Article 7. Activities of the Adviser. The services of the Adviser to the
Fund are not deemed to be exclusive, the Adviser being free to render investment
advisory and/or other services to others. The Adviser may permit other fund
clients to use the initials "MFS" in their names. The Fund agrees that if the
Adviser shall for any reason no longer serve as the Adviser to the Fund, the
Fund will change its name so as to delete the initials "MFS." It is understood
that the Trustees, officers and shareholders of the Trust are or may be or
become interested in the Adviser, as Directors, officers, employees, or
otherwise and that Directors, officers and employees of the Adviser are or may
become similarly interested in the Trust, and that the Adviser may be or become
interested in the Fund as a shareholder or otherwise.

Article 8. Duration, Termination and Amendment of this Agreement. This
Agreement shall become effective on the date first above written and shall
govern the relations between the parties hereto thereafter, and shall remain in
force until November 1, 2001 on which date it will terminate unless its
continuance after November 1, 2001 is "specifically approved at least annually"
(i) by the vote of a majority of the Trustees of the Trust who are not
"interested persons" of the Trust or of the Adviser at a meeting specifically
called for the purpose of voting on such approval, and (ii) by the Board of
Trustees of the Trust, or by "vote of a majority of the outstanding voting
securities" of the Fund.

This Agreement may be terminated at any time without the payment of any
penalty by the Trustees or by "vote of a majority of the outstanding voting
securities" of the Fund, or by the Adviser, in each case on not more than sixty
days' nor less than thirty days' written notice to the other party. This
Agreement shall automatically terminate in the event of its "assignment".

This Agreement may be amended only if such amendment is approved by "vote
of a majority of the outstanding voting securities" of the Fund.

Article 9. Scope of Trust's Obligations. A copy of the Trust's Declaration
of Trust is on file with the Secretary of State of The Commonwealth of
Massachusetts. The Adviser acknowledges that the obligations of or arising out
of this Agreement are not binding upon any of the Trust's trustees, officers,
employees, agents or shareholders individually, but are binding solely upon the
assets and property of the Trust. If this Agreement is executed by the Trust on
behalf of one or more series of the Trust, the Adviser further acknowledges that
the assets and liabilities of each series of the Trust are separate and distinct
and that the obligations of or arising out of this Agreement are binding solely
upon the assets or property of the series on whose behalf the Trust has executed
this Agreement.

Article 10. Definitions. The terms "specifically approved at least
annually," "vote of a majority of the outstanding voting securities,"
"assignment," "affiliated

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person," and "interested person," when used in this Agreement, shall have the
respective meanings specified, and shall be construed in a manner consistent
with, the Investment Company Act of 1940 and the Rules and Regulations
promulgated thereunder, subject, however, to such exemptions as may be granted
by the Securities and Exchange Commission under said Act.

Article 11. Record Keeping. The Adviser will maintain records in a form
acceptable to the Trust and in compliance with the rules and regulations of the
Securities and Exchange Commission, including but not limited to records
required to be maintained by Section 31(a) of the Investment Company Act of 1940
and the rules thereunder, which at all times will be the property of the Trust
and will be available for inspection and use by the Trust.

IN WITNESS WHEREOF, the parties have caused this Agreement to be executed
and delivered in their names and on their behalf by the undersigned, thereunto
duly authorized, all as of the day and year first written above. The undersigned
Trustee of the Trust has executed this Agreement not individually, but as
Trustee under the Declaration.

MFS/SUN LIFE SERIES TRUST, on
behalf of STRATEGIC GROWTH SERIES,
one of its series

By:____________________________________
John D. McNeil
Chairman and Trustee

MASSACHUSETTS FINANCIAL SERVICES COMPANY

By:____________________________________
Arnold D. Scott
Senior Executive Vice President
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<PAGE>
EXHIBIT NO. 99.9(b)

LEGAL OPINION CONSENT

I consent to the incorporation by reference in this Post-Effective Amendment No.
24 to the Registration Statement (File Nos. 2-83616 and 811-3732) (the
"Registration Statement") of MFS/Sun Life Series Trust (the "Trust"), of my
opinion dated April 24, 1998, appearing in Post-Effective Amendment No. 22 to
the Trust's Registration Statement, which was filed with the Securities and
Exchange Commission on April 29, 1998.

JAMES R. BORDEWICK, JR.
James R. Bordewick, Jr.
Assistant Secretary

Boston, Massachusetts
August 11, 1999
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