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Ex-99.CERT
MFS/SUN LIFE SERIES TRUST
CERTIFICATION PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT
I, Richard M. Hisey, certify that:
1. I have reviewed this report on Form N-CSR of MFS/Sun Life Series
Trust;
2. Based on my knowledge, this report does not contain any untrue
statement of a material fact or omit to state a material fact
necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect to
the period covered by this report;
3. Based on my knowledge, the financial statements, and other financial
information included in this report, fairly present in all material
respects the financial condition, results of operations, changes in
net assets, and cash flows (if the financial statements are required
to include a statement of cash flows) of the registrant as of, and
for, the periods presented in this report;
4. The registrant's other certifying officers and I are responsible for
establishing and maintaining disclosure controls and procedures (as
defined in Rule 30a-3(c) under the Investment Company Act of 1940) and
internal control over financial reporting (as defined in Rule 30a-3(d)
under the Investment Company Act of 1940) for the registrant and have:
a. designed such disclosure controls and procedures, or caused
such disclosure controls and procedures to be designed under
our supervision, to ensure that material information relating
to the registrant, including its consolidated subsidiaries, is
made known to us by others within those entities, particularly
during the period in which this report is being prepared;
b. designed such internal control over financial reporting, or
caused such internal control over financial reporting to be
designed under our supervision, to provide reasonable assurance
regarding the reliability of financial reporting and the
preparation of financial statements for external purposes in
accordance with generally accepted accounting principles;
c. evaluated the effectiveness of the registrant's disclosure
controls and procedures and presented in this report our
conclusions about the effectiveness of the disclosure controls
and procedures as of a date within 90 days prior to the filing
date of this report based on such evaluation; and
d. disclosed in this report any change in the registrant's
internal control over financial reporting that occurred during
the second fiscal quarter of the period covered by the report
that has materially affected, or is reasonably likely to
materially affect, the registrant's internal control over
financial reporting; and
5. The registrant's other certifying officers and I have disclosed to the
registrant's auditors and the audit committee of the registrant's
board of directors (or persons performing the equivalent functions):
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a. all significant deficiencies and material weaknesses in the
design or operation of internal control over financial reporting
which are reasonably likely to adversely affect the registrant's
ability to record, process, summarize, and report financial
information; and
b. any fraud, whether or not material, that involves management or
other employees who have a significant role in the registrant's
internal control over financial reporting.
Date: February 24, 2005 RICHARD M. HISEY
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Richard M. Hisey
Treasurer (Principal Financial Officer and
Accounting Officer)
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MFS/SUN LIFE SERIES TRUST
CERTIFICATION PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT
I, Robert J. Manning, certify that:
1. I have reviewed this report on Form N-CSR of MFS/Sun Life Series
Trust;
2. Based on my knowledge, this report does not contain any untrue
statement of a material fact or omit to state a material fact
necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect to
the period covered by this report;
3. Based on my knowledge, the financial statements, and other financial
information included in this report, fairly present in all material
respects the financial condition, results of operations, changes in
net assets, and cash flows (if the financial statements are required
to include a statement of cash flows) of the registrant as of, and
for, the periods presented in this report;
4. The registrant's other certifying officers and I are responsible for
establishing and maintaining disclosure controls and procedures (as
defined in Rule 30a-3(c) under the Investment Company Act of 1940) and
internal control over financial reporting (as defined in Rule 30a-3(d)
under the Investment Company Act of 1940) for the registrant and have:
a. designed such disclosure controls and procedures, or caused such
disclosure controls and procedures to be designed under our
supervision, to ensure that material information relating to the
registrant, including its consolidated subsidiaries, is made
known to us by others within those entities, particularly during
the period in which this report is being prepared;
b. designed such internal control over financial reporting, or
caused such internal control over financial reporting to be
designed under our supervision, to provide reasonable assurance
regarding the reliability of financial reporting and the
preparation of financial statements for external purposes in
accordance with generally accepted accounting principles;
c. evaluated the effectiveness of the registrant's disclosure
controls and procedures and presented in this report our
conclusions about the effectiveness of the disclosure controls
and procedures as of a date within 90 days prior to the filing
date of this report based on such evaluation; and
d. disclosed in this report any change in the registrant's internal
control over financial reporting that occurred during the second
fiscal quarter of the period covered by the report that has
materially affected, or is reasonably likely to materially
affect, the registrant's internal control over financial
reporting; and
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5. The registrant's other certifying officers and I have disclosed to the
registrant's auditors and the audit committee of the registrant's
board of directors (or persons performing the equivalent functions):
a. all significant deficiencies and material weaknesses in the
design or operation of internal control over financial reporting
which are reasonably likely to adversely affect the registrant's
ability to record, process, summarize, and report financial
information; and
b. any fraud, whether or not material, that involves management or
other employees who have a significant role in the registrant's
internal control over financial reporting.
Date: February 24, 2005 ROBERT J. MANNING
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Robert J. Manning
President (Principal Executive Officer)