Exhibit 99.1350CERT

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

      I, Terry K. Glenn, President of Merrill Lynch Large Cap Core 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: June 23, 2003


                                               /s/ Terry K. Glenn
                                               ------------------
                                               Terry K. Glenn,
                                               President of
                                               Merrill Lynch Large Cap Core Fund

      A signed original of this written statement required by Section 906 has
      been provided to Merrill Lynch Large Cap Core Fund and will be retained by
      Merrill Lynch Large Cap Core Fund and furnished to the Securities and
      Exchange Commission or staff upon request.



Exhibit 99.1350CERT

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

      I, Donald C. Burke, Chief Financial Officer of Merrill Lynch Large Cap
      Core 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: June 23, 2003


                                               /s/ Donald C. Burke
                                               -------------------
                                               Donald C. Burke,
                                               Chief Financial Officer of
                                               Merrill Lynch Large Cap Core Fund

      A signed original of this written statement required by Section 906 has
      been provided to Merrill Lynch Large Cap Core Fund and will be retained by
      Merrill Lynch Large Cap Core Fund and furnished to the Securities and
      Exchange Commission or staff upon request.