Exhibit 99.1350CERT

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

      I, Terry K. Glenn, President of Merrill Lynch Municipal Intermediate Term
      Fund of Merrill Lynch Municipal Series Trust (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 18, 2004


                                        /s/ Terry K. Glenn
                                        ------------------
                                        Terry K. Glenn,
                                        President of
                                        Merrill Lynch Municipal Intermediate
                                        Term Fund of Merrill Lynch Municipal
                                        Series Trust

      A signed original of this written statement required by Section 906, or
      other document authenticating, acknowledging, or otherwise adopting the
      signature that appears in typed form within the electronic version of this
      written statement required by Section 906, has been provided to Merrill
      Lynch Municipal Intermediate Term Fund of Merrill Lynch Municipal Series
      Trust and will be retained by Merrill Lynch Municipal Intermediate Term
      Fund of Merrill Lynch Municipal Series Trust and furnished to the
      Securities and Exchange Commission or its 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 Municipal
      Intermediate Term Fund of Merrill Lynch Municipal Series Trust (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 18, 2004


                                        /s/ Donald C. Burke
                                        -------------------
                                        Donald C. Burke,
                                        Chief Financial Officer of
                                        Merrill Lynch Municipal Intermediate
                                        Term Fund of Merrill Lynch Municipal
                                        Series Trust

      A signed original of this written statement required by Section 906, or
      other document authenticating, acknowledging, or otherwise adopting the
      signature that appears in typed form within the electronic version of this
      written statement required by Section 906, has been provided to Merrill
      Lynch Municipal Intermediate Term Fund of Merrill Lynch Municipal Series
      Trust and will be retained by Merrill Lynch Municipal Intermediate Term
      Fund of Merrill Lynch Municipal Series Trust and furnished to the
      Securities and Exchange Commission or its staff upon request.