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                                                           Exhibit 99.906 CERT

                        State Street Research Capital Trust
                                  Certification
            Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002
             (Subsections (a) and (b) of Section 1350, Chapter 63 of
                          Title 18, United States Code)

Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, the undersigned
officer of the State Street Research Capital Trust, a Massachusetts
business trust, (the "Trust"), does hereby certify that the Trust's report on
Form N-CSR for the period ended September 30, 2004 (the "N-CSR") fully
complies with the requirements of Section 13 (a) or 15 (d), as applicable, of
the Securities Exchange Act of 1934, as amended, and information contained in
the N-CSR fairly presents, in all material respects, the financial condition
and the results of operations of the Trust. This certification is provided
solely pursuant to 18 U.S.C. 1350 and shall not be deemed a part of the
N-CSR, the financial statements filed with the N-CSR or otherwise "filed" for
any purpose.

Date: December 7, 2004


                                          /s/ Douglas A. Romich
                                          Douglas A. Romich
                                          Treasurer

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                        State Street Research Capital Trust
                                  Certification
           Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002
            (Subsections (a) and (b) of Section 1350, Chapter 63 of
                         Title 18, United States Code)

Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, the undersigned
officer of the State Street Research Capital Trust, a Massachusetts
business trust, (the "Trust"), does hereby certify that the Trust's report on
Form N-CSR for the period ended September 30, 2004 (the "N-CSR") fully
complies with the requirements of Section 13 (a) or 15 (d), as applicable, of
the Securities Exchange Act of 1934, as amended, and information contained in
the N-CSR fairly presents, in all material respects, the financial condition
and the results of operations of the Trust. This certification is provided
solely pursuant to 18 U.S.C. 1350 and shall not be deemed a part of the
N-CSR, the financial statements filed with the N-CSR or otherwise "filed" for
any purpose.

Date: December 7, 2004


                                /s/ Richard S. Davis
                                Richard S. Davis
                                President, Chairman and Chief Executive Officer