Exhibit 99.1350CERT

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

I, Terry K. Glenn, President of Merrill Lynch California Insured Municipal Bond
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: April 21, 2003

                                                /s/ Terry K. Glenn
                                                --------------------------------
                                                Terry K. Glenn,
                                                President of
                                                Merrill Lynch California Insured
                                                Municipal Bond Fund


Exhibit 99.1350CERT

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

I, Donald C. Burke, Chief Financial Officer of Merrill Lynch California Insured
Municipal Bond 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: April 21, 2003

                                                /s/ Donald C. Burke
                                                --------------------------------
                                                Donald C. Burke,
                                                Chief Financial Officer of
                                                Merrill Lynch California Insured
                                                Municipal Bond Fund