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                                                              Exhibit 99.906CERT

                            SECTION 906 CERTIFICATION

                Certification Pursuant to 18 U.S.C. Section 1350,
                             As Adopted Pursuant to
                  Section 906 of the Sarbanes-Oxley Act of 2002

Morgan Stanley Select Dimensions Investment Series

       In connection with the Report on Form N-CSR (the "Report") of the
above-named issuer for the period ended December 31, 2004 that is accompanied by
this certification, the undersigned hereby certifies that:

1.     The Report fully complies with the requirements of Section 13(a) or 15(d)
       of the Securities Exchange Act of 1934; and

2.     The information contained in the Report fairly presents, in all material
       respects, the financial condition and results of operations of the
       Issuer.


Date: February 17, 2005                         /s/ Ronald E. Robison
                                                ---------------------
                                                Ronald E. Robison
                                                Principal Executive Officer


A signed original of this written statement required by Section 906 has been
provided to Morgan Stanley Select Dimensions Investment Series and will be
retained by Morgan Stanley Select Dimensions Investment Series and furnished to
the Securities and Exchange Commission or its staff upon request.

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                            SECTION 906 CERTIFICATION

                Certification Pursuant to 18 U.S.C. Section 1350,
                             As Adopted Pursuant to
                  Section 906 of the Sarbanes-Oxley Act of 2002

Morgan Stanley Select Dimensions Investment Series

       In connection with the Report on Form N-CSR (the "Report") of the
above-named issuer for the period ended December 31, 2004 that is accompanied by
this certification, the undersigned hereby certifies that:

1.     The Report fully complies with the requirements of Section 13(a) or 15(d)
       of the Securities Exchange Act of 1934; and

2.     The information contained in the Report fairly presents, in all material
       respects, the financial condition and results of operations of the
       Issuer.


Date: February 17, 2005                         /s/ Francis Smith
                                                -----------------
                                                Francis Smith
                                                Principal Financial Officer


A signed original of this written statement required by Section 906 has been
provided to Morgan Stanley Select Dimensions Investment Series and will be
retained by Morgan Stanley Select Dimensions Investment Series and furnished to
the Securities and Exchange Commission or its staff upon request.