Exhibit 99.1

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

I, Donald C. Burke, Chief Financial Officer of Merrill Lynch International Index
Fund (the "Fund"), certify that:

      1.    The N-CSR of the Fund (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 Fund.

Dated: February 24, 2003

                                          /s/ Donald C. Burke
                                          --------------------------------------
                                          Donald C. Burke,
                                          Chief Financial Officer of
                                          Merrill Lynch International Index Fund



Exhibit 99.1

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

I, Terry K. Glenn, President of Merrill Lynch International Index Fund (the
"Fund"), certify that:

      1.    The N-CSR of the Fund (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 Fund.

Dated: February 24, 2003

                                          /s/ Terry K. Glenn
                                          --------------------------------------
                                          Terry K. Glenn,
                                          President of
                                          Merrill Lynch International Index Fund