EX-99. CERT

                      CERTIFICATION PURSUANT TO SECTION 302
                        OF THE SARBANES-OXLEY ACT OF 2002

- --------------------------------------------------------------------------------

I, Terry K. Glenn, President of WCMA Government Securities Fund and Master
Government Securities Trust, certify that:

      1.    I have reviewed this report on Form N-CSR of WCMA Government
            Securities Fund and Master Government Securities Trust (together,
            the "Fund");

      2.    Based on my knowledge, this report does not contain any untrue
            statement of a material fact or omit to state a material fact
            necessary to make the statements made, in light of the circumstances
            under which such statements were made, not misleading with respect
            to the period covered by this report;

      3.    Based on my knowledge, the financial statements, and other financial
            information included in this report, fairly present in all material
            respects the financial condition, results of operations, changes in
            net assets, and cash flows (if the financial statements are required
            to include a statement of cash flows) of the Fund as of, and for,
            the periods presented in this report;

      4.    The Fund's other certifying officer(s) and I are responsible for
            establishing and maintaining disclosure controls and procedures (as
            defined in Rule 30a-3(c) under the Investment Company Act of 1940)
            and internal control over financial reporting (as defined in Rule
            30a-3(d) under the Investment Company Act of 1940) for the Fund and
            have:

            a)    designed such disclosure controls and procedures, or caused
                  such disclosure controls and procedures to be designed under
                  our supervision, to ensure that material information relating
                  to the Fund, including its consolidated subsidiaries, is made
                  known to us by others within those entities, particularly
                  during the period in which this report is being prepared;

            b)    evaluated the effectiveness of the Fund's disclosure controls
                  and procedures and presented in this report our conclusions
                  about the effectiveness of the disclosure controls and
                  procedures, as of a date within 90 days prior to the filing
                  date of this report based on such evaluation; and



            c)    disclosed in this report any change in the Fund's internal
                  control over financial reporting that occurred during the
                  Fund's most recent fiscal half-year (the Fund's second fiscal
                  half-year in the case of an annual report) that has materially
                  affected, or is reasonably likely to materially affect, the
                  Fund's internal control over financial reporting; and

      5.    The Fund's other certifying officer(s) and I have disclosed to the
            Fund's auditors and the audit committee of the Fund's board of
            directors (or persons performing the equivalent functions):

            a)    all significant deficiencies and material weaknesses in the
                  design or operation of internal control over financial
                  reporting which are reasonably likely to adversely affect the
                  Fund's ability to record, process, summarize, and report
                  financial information; and

            b)    any fraud, whether or not material, that involves management
                  or other employees who have a significant role in the Fund's
                  internal control over financial reporting.

      Date: November 19, 2004


                                        /s/ Terry K. Glenn
                                        ------------------
                                        Terry K. Glenn,
                                        President of WCMA Government Securities
                                        Fund and Master Government Securities
                                        Trust



EX-99. CERT

                      CERTIFICATION PURSUANT TO SECTION 302
                        OF THE SARBANES-OXLEY ACT OF 2002

- --------------------------------------------------------------------------------

I, Donald C. Burke, Chief Financial Officer of WCMA Government Securities Fund
and Master Government Securities Trust, certify that:

      1.    I have reviewed this report on Form N-CSR of WCMA Government
            Securities Fund and Master Government Securities Trust (together,
            the "Fund");

      2.    Based on my knowledge, this report does not contain any untrue
            statement of a material fact or omit to state a material fact
            necessary to make the statements made, in light of the circumstances
            under which such statements were made, not misleading with respect
            to the period covered by this report;

      3.    Based on my knowledge, the financial statements, and other financial
            information included in this report, fairly present in all material
            respects the financial condition, results of operations, changes in
            net assets, and cash flows (if the financial statements are required
            to include a statement of cash flows) of the Fund as of, and for,
            the periods presented in this report;

      4.    The Fund's other certifying officer(s) and I are responsible for
            establishing and maintaining disclosure controls and procedures (as
            defined in Rule 30a-3(c) under the Investment Company Act of 1940)
            and internal control over financial reporting (as defined in Rule
            30a-3(d) under the Investment Company Act of 1940) for the Fund and
            have:

            a)    designed such disclosure controls and procedures, or caused
                  such disclosure controls and procedures to be designed under
                  our supervision, to ensure that material information relating
                  to the Fund, including its consolidated subsidiaries, is made
                  known to us by others within those entities, particularly
                  during the period in which this report is being prepared;

            b)    evaluated the effectiveness of the Fund's disclosure controls
                  and procedures and presented in this report our conclusions
                  about the effectiveness of the disclosure controls and
                  procedures, as of a date within 90 days prior to the filing
                  date of this report based on such evaluation; and



            c)    disclosed in this report any change in the Fund's internal
                  control over financial reporting that occurred during the
                  Fund's most recent fiscal half-year (the Fund's second fiscal
                  half-year in the case of an annual report) that has materially
                  affected, or is reasonably likely to materially affect, the
                  Fund's internal control over financial reporting; and

      5.    The Fund's other certifying officer(s) and I have disclosed to the
            Fund's auditors and the audit committee of the Fund's board of
            directors (or persons performing the equivalent functions):

            a)    all significant deficiencies and material weaknesses in the
                  design or operation of internal control over financial
                  reporting which are reasonably likely to adversely affect the
                  Fund's ability to record, process, summarize, and report
                  financial information; and

            b)    any fraud, whether or not material, that involves management
                  or other employees who have a significant role in the Fund's
                  internal control over financial reporting.

      Date: November 19, 2004


                                                /s/ Donald C. Burke
                                                -------------------
                                                Donald C. Burke,
                                                Chief Financial Officer of
                                                WCMA Government Securities Fund
                                                and Master Government Securities
                                                Trust