Exhibit 99.1350CERT

         Certification Pursuant to Section 906 of the Sarbanes Oxley Act

I, Robert C. Doll, Jr., Chief Executive Officer of CMA Government Securities
Fund and Master Government Securities Trust (together, 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: November 17, 2006


                                                  /s/ Robert C. Doll, Jr.
                                                  ------------------------------
                                                  Robert C. Doll, Jr.,
                                                  Chief Executive Officer of
                                                  CMA Government Securities Fund
                                                  and Master Government
                                                  Securities 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 CMA Government Securities Fund and
Master Government Securities Trust and will be retained by CMA Government
Securities Fund and Master Government Securities 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 CMA Government Securities Fund
and Master Government Securities Trust (together, 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: November 17, 2006


                                                  /s/ Donald C. Burke
                                                  ------------------------------
                                                  Donald C. Burke,
                                                  Chief Financial Officer of
                                                  CMA Government Securities Fund
                                                  and Master Government
                                                  Securities 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 CMA Government Securities Fund and
Master Government Securities Trust and will be retained by CMA Government
Securities Fund and Master Government Securities Trust and furnished to the
Securities and Exchange Commission or its staff upon request.