<Page>
EXHIBIT B1
CERTIFICATION OF PRINCIPAL EXECUTIVE OFFICER
CERTIFICATIONS
I, Ronald E. Robison, certify that:
1. I have reviewed this report on Form N-CSR of Morgan Stanley Select
Dimensions Investment Series;
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-2(c) under the Investment Company Act of
1940) for the registrant and have:
a) designed such disclosure controls and procedures 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) evaluated the effectiveness of the registrant's disclosure controls
and procedures as of a date within 90 days prior to the filing date
of this report (the "Evaluation Date"); and
c) presented in this report our conclusions about the effectiveness of
the disclosure controls and procedures based on our evaluation as
of the Evaluation Date;
3
<Page>
5. The registrant's other certifying officers and I have disclosed,
based on our most recent evaluation, 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 in the design or operation of internal
controls which could adversely affect the registrant's ability to
record, process, summarize, and report financial data and have
identified for the registrant's auditors any material weaknesses in
internal controls; and
b) any fraud, whether or not material, that involves management or
other employees who have a significant role in the registrant's
internal controls; and
6. The registrant's other certifying officers and I have indicated in
this report whether or not there were significant changes in
internal controls or in other factors that could significantly
affect internal controls subsequent to the date of our most recent
evaluation, including any corrective actions with regard to
significant deficiencies and material weaknesses.
Date: August 19, 2003
Ronald E. Robison
Principal Executive Officer
4
<Page>
EXHIBIT B2
CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER
CERTIFICATIONS
I, Francis Smith, certify that:
1. I have reviewed this report on Form N-CSR of Morgan Stanley Select
Dimensions Investment Series;
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-2(c) under the Investment Company Act of
1940) for the registrant and have:
(i) designed such disclosure controls and procedures 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;
(ii) evaluated the effectiveness of the registrant's disclosure
controls and procedures as of a date within 90 days prior to the
filing date of this report (the "Evaluation Date"); and
(iii) presented in this report our conclusions about the effectiveness
of the disclosure controls and procedures based on our
evaluation as of the Evaluation Date;
5. The registrant's other certifying officers and I have disclosed,
based on our most recent evaluation, to the registrant's auditors
and the audit committee of the registrant's board of directors (or
persons performing the equivalent functions):
5
<Page>
a) all significant deficiencies in the design or operation of internal
controls which could adversely affect the registrant's ability to
record, process, summarize, and report financial data and have
identified for the registrant's auditors any material weaknesses in
internal controls; and
b) any fraud, whether or not material, that involves management or
other employees who have a significant role in the registrant's
internal controls; and
6. The registrant's other certifying officers and I have indicated in
this report whether or not there were significant changes in
internal controls or in other factors that could significantly
affect internal controls subsequent to the date of our most recent
evaluation, including any corrective actions with regard to
significant deficiencies and material weaknesses.
Date: August 19, 2003
Francis Smith
Principal Financial Officer
6