Exhibit 4(a)

                         INVESTMENT MANAGEMENT AGREEMENT

      AGREEMENT, dated September 29, 2006, between Master Government Securities
Trust (the "Trust"), a Delaware statutory trust, and BlackRock Advisors, LLC
(the "Advisor"), a Delaware limited liability company.

      WHEREAS, the Advisor has agreed to furnish investment advisory services to
the Trust, an open-end management investment company registered under the
Investment Company Act of 1940, as amended (the "1940 Act");

      WHEREAS, this Agreement has been approved in accordance with the
provisions of the 1940 Act, and the Advisor is willing to furnish such services
upon the terms and conditions herein set forth;

      WHEREAS, the Trust serves as the "master" portfolio for one or more
"feeder" funds that invest their assets in the Trust and that have the same
investment objective and policies as the Trust;

      NOW, THEREFORE, in consideration of the mutual premises and covenants
herein contained and other good and valuable consideration, the receipt of which
is hereby acknowledged, it is agreed by and between the parties hereto as
follows:

      1. In General. The Advisor agrees, all as more fully set forth herein, to
act as investment advisor to the Trust with respect to the investment of the
Trust's assets and to supervise and arrange for the day to day operations of the
Trust and the purchase of securities for and the sale of securities held in the
investment portfolio of the Trust.

      2. Duties and Obligations of the Advisor with Respect to Investment of
Assets of the Trust. Subject to the succeeding provisions of this section and
subject to the direction and control of the Trust's Board of Trustees, the
Advisor shall (i) act as investment advisor for and supervise and manage the
investment and reinvestment of the Trust's assets and in connection therewith
have complete discretion in purchasing and selling securities and other assets
for the Trust and in voting, exercising consents and exercising all other rights
appertaining to such securities and other assets on behalf of the Trust; (ii)
supervise continuously the investment program of the Trust and the composition
of its investment portfolio; (iii) arrange, subject to the provisions of
paragraph 4 hereof, for the purchase and sale of securities and other assets
held in the investment portfolio of the Trust; and (iv) provide investment
research to the Trust.

      3. Duties and Obligations of the Advisor with Respect to the
Administration of the Trust. The Advisor also agrees to furnish office
facilities and equipment and clerical, bookkeeping and administrative services
(other than such services, if any, provided by the Trust's Custodian, Transfer
Agent and Dividend Disbursing Agent and other service providers) for the Trust.
To the extent requested by the Trust, the Advisor agrees to provide the
following administrative services:

            (a) Oversee the determination and publication of the Trust's net
      asset value in accordance with the Trust's policy as adopted from time to
      time by the Board of Trustees;

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            (b) Oversee the maintenance by the Trust's Custodian and Transfer
      Agent and Dividend Disbursing Agent of certain books and records of the
      Trust as required under Rule 31a-1(b) under the 1940 Act and maintain (or
      oversee maintenance by such other persons as are approved by the Board of
      Trustees) such other books and records required by law or for the proper
      operation of the Trust;

            (c) Oversee the preparation and filing of the Trust's federal, state
      and local income tax returns and any other required tax returns;

            (d) Review the appropriateness of and arrange for payment of the
      Trust's expenses;

            (e) Prepare for review and approval by officers of the Trust
      financial information for the Trust's semiannual and annual reports, proxy
      statements and other communications with shareholders required or
      otherwise to be sent to Trust shareholders, and arrange for the printing
      and dissemination of such reports and communications to shareholders;

            (f) Prepare for review by an officer of the Trust the Trust's
      periodic financial reports required to be filed with the Securities and
      Exchange Commission ("SEC") on Form N-SAR, Form N-CSR, Form N-PX, Form
      N-Q, and such other reports, forms and filings, as may be mutually agreed
      upon;

            (g) Prepare such reports relating to the business and affairs of the
      Trust as may be mutually agreed upon and not otherwise appropriately
      prepared by the Trust's custodian, counsel or auditors;

            (h) Make such reports and recommendations to the Board of Trustees
      concerning the performance of the independent accountants as the Board of
      Trustees may reasonably request or deems appropriate;

            (i) Make such reports and recommendations to the Board of Trustees
      concerning the performance and fees of the Trust's Custodian and Transfer
      Agent and Dividend Disbursing Agent as the Board of Trustees may
      reasonably request or deems appropriate;

            (j) Oversee and review calculations of fees paid to the Trust's
      service providers;

            (k) Oversee the Trust's portfolio and perform necessary calculations
      as required under Section 18 of the 1940 Act;

            (l) Consult with the Trust's officers, independent accountants,
      legal counsel, custodian, accounting agent and transfer and dividend
      disbursing agent in establishing the accounting policies of the Trust and
      monitor financial and shareholder accounting services;

            (m) Determine the amounts available for distribution as dividends
      and distributions to be paid by the Trust to its shareholders; prepare and
      arrange for the printing of dividend notices to shareholders; and provide
      the Trust's dividend disbursing agent and


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      custodian with such information as is required for such parties to effect
      the payment of dividends and distributions and to implement the Trust's
      dividend reinvestment plan;

            (n) Prepare such information and reports as may be required by any
      banks from which a Trust borrows funds;

            (o) Provide such assistance to the Custodian and the Trust's counsel
      and auditors as generally may be required to properly carry on the
      business and operations of the Trust;

            (p) Respond to or refer to the Trust's officers or transfer agent,
      shareholder (including any potential shareholder) inquiries relating to
      the Trust; and

            (q) Supervise any other aspects of the Trust's administration as may
      be agreed to by the Trust and the Advisor.

      All services are to be furnished through the medium of any trustees,
officers or employees of the Advisor or its affiliates as the Advisor deems
appropriate in order to fulfill its obligations hereunder.

      The Trust will reimburse the Advisor or its affiliates for all out of
pocket expenses incurred by them in connection with the performance of the
administrative services described in this paragraph 3. The Trust will reimburse
the Advisor and its affiliates for their costs in providing accounting services
to the Trust.

      4. Covenants. (a) In the performance of its duties under this Agreement,
the Advisor shall at all times conform to, and act in accordance with, any
requirements imposed by: (i) the provisions of the 1940 Act and the Investment
Advisers Act of 1940, as amended, and all applicable Rules and Regulations of
the Securities and Exchange Commission; (ii) any other applicable provision of
law; (iii) the provisions of the Declaration of Trust and By Laws of the Trust,
as such documents are amended from time to time; (iv) the investment objectives
and policies of the Trust as set forth in the Trust's Registration Statement on
Form N-1A and/or the resolutions of the Board of Trustees; and (v) any policies
and determinations of the Board of Trustees of the Trust.

            (b) In addition, the Advisor will:

                  (i) place orders either directly with the issuer or with any
            broker or dealer. Subject to the other provisions of this paragraph,
            in placing orders with brokers and dealers, the Advisor will attempt
            to obtain the best price and the most favorable execution of its
            orders. In placing orders, the Advisor will consider the experience
            and skill of the firm's securities traders as well as the firm's
            financial responsibility and administrative efficiency. Consistent
            with this obligation, the Advisor may select brokers on the basis of
            the research, statistical and pricing services they provide to the
            Trust and other clients of the Advisor. Information and research
            received from such brokers will be in addition to, and not in lieu
            of, the services required to be performed by the Advisor hereunder.
            A commission paid to such brokers may be higher than that which
            another qualified broker would have charged for effecting the same
            transaction, provided that the Advisor determines in good faith that
            such commission is


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            reasonable in terms either of the transaction or the overall
            responsibility of the Advisor to the Trust and its other clients and
            that the total commissions paid by the Trust will be reasonable in
            relation to the benefits to the Trust over the long term. Subject to
            the foregoing and the provisions of the 1940 Act, the Securities
            Exchange Act of 1934, as amended, and other applicable provisions of
            law, the Advisor may select brokers and dealers with which it or the
            Trust is affiliated;

                  (ii) maintain a policy and practice of conducting its
            investment advisory services hereunder independently of the
            commercial banking operations of its affiliates. When the Advisor
            makes investment recommendations for the Trust, its investment
            advisory personnel will not inquire or take into consideration
            whether the issuer of securities proposed for purchase or sale for
            the Trust's account are customers of the commercial department of
            its affiliates; and

                  (iii) treat confidentially and as proprietary information of
            the Trust all records and other information relative to the Trust,
            and the Trust's prior, current or potential shareholders, and will
            not use such records and information for any purpose other than
            performance of its responsibilities and duties hereunder, except
            after prior notification to and approval in writing by the Trust,
            which approval shall not be unreasonably withheld and may not be
            withheld where the Advisor may be exposed to civil or criminal
            contempt proceedings for failure to comply, when requested to
            divulge such information by duly constituted authorities, or when so
            requested by the Trust.

      5. Services Not Exclusive. Nothing in this Agreement shall prevent the
Advisor or any officer, employee or other affiliate thereof from acting as
investment advisor for any other person, firm or corporation, or from engaging
in any other lawful activity, and shall not in any way limit or restrict the
Advisor or any of its officers, employees or agents from buying, selling or
trading any securities for its or their own accounts or for the accounts of
others for whom it or they may be acting; provided, however, that the Advisor
will undertake no activities which, in its judgment, will adversely affect the
performance of its obligations under this Agreement.

      6. Sub-Advisors. The Advisor may from time to time, in its sole discretion
to the extent permitted by applicable law, appoint one or more sub-advisors,
including, without limitation, affiliates of the Advisor, to perform investment
advisory services with respect to the Trust. The Advisor may terminate any or
all sub-advisors in its sole discretion at any time to the extent permitted by
applicable law.

      7. Books and Records. In compliance with the requirements of Rule 31a-3
under the 1940 Act, the Advisor hereby agrees that all records which it
maintains for the Trust are the property of the Trust and further agrees to
surrender promptly to the Trust any such records upon the Trust's request. The
Advisor further agrees to preserve for the periods prescribed by Rule 31a-2
under the 1940 Act the records required to be maintained by Rule 31a-1 under the
1940 Act.

      8. Expenses. During the term of this Agreement, the Advisor will bear all
costs and expenses of its employees and any overhead incurred in connection with
its duties hereunder and shall bear the costs of any salaries or trustees' fees
of any officers or Trustees of the Trust who


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are affiliated persons (as defined in the 1940 Act) of the Advisor; provided
that the Board of Trustees of the Trust may approve reimbursement to the Advisor
of the pro rata portion of the salaries, bonuses, health insurance, retirement
benefits and all similar employment costs for the time spent on Trust operations
(including, without limitation, compliance matters) (other than the provision of
investment advice and administrative services required to be provided hereunder)
of all personnel employed by the Advisor who devote substantial time to Trust
operations or the operations of other investment companies advised by the
Advisor.

      9. Compensation of the Advisor. (a) The Trust agrees to pay to the Advisor
and the Advisor agrees to accept as full compensation for all services rendered
by the Advisor as such, a monthly fee (the "Investment Advisory Fee") in arrears
at an annual rate equal to the amount set forth in Schedule A hereto of the
average daily value of the Trust's Net Assets. "Net Assets" means the total
assets of a Trust minus the sum of the accrued liabilities. For any period less
than a month during which this Agreement is in effect, the fee shall be prorated
according to the proportion which such period bears to a full month of 28, 29,
30 or 31 days, as the case may be.

            (b) For purposes of this Agreement, the net assets of the Trust
      shall be calculated pursuant to the procedures adopted by resolutions of
      the Trustees of the Trust for calculating the value of the Trust's assets
      or delegating such calculations to third parties.

      10. Indemnity. (a) The Trust may, in the discretion of the Board of
Trustees of the Trust, indemnify the Advisor, and each of the Advisor's
trustees, officers, employees, agents, associates and controlling persons and
the trustees, partners, members, officers, employees and agents thereof
(including any individual who serves at the Advisor's request as director,
officer, partner, member, trustee or the like of another entity) (each such
person being an "Indemnitee") against any liabilities and expenses, including
amounts paid in satisfaction of judgments, in compromise or as fines and
penalties, and counsel fees (all as provided in accordance with applicable state
law) reasonably incurred by such Indemnitee in connection with the defense or
disposition of any action, suit or other proceeding, whether civil or criminal,
before any court or administrative or investigative body in which such
Indemnitee may be or may have been involved as a party or otherwise or with
which such Indemnitee may be or may have been threatened, while acting in any
capacity set forth herein or thereafter by reason of such Indemnitee having
acted in any such capacity, except with respect to any matter as to which such
Indemnitee shall have been adjudicated not to have acted in good faith in the
reasonable belief that such Indemnitee's action was in the best interest of the
Trust and furthermore, in the case of any criminal proceeding, so long as such
Indemnitee had no reasonable cause to believe that the conduct was unlawful;
provided, however, that (1) no Indemnitee shall be indemnified hereunder against
any liability to the Trust or its shareholders or any expense of such Indemnitee
arising by reason of (i) willful misfeasance, (ii) bad faith, (iii) gross
negligence or (iv) reckless disregard of the duties involved in the conduct of
such Indemnitee's position (the conduct referred to in such clauses (i) through
(iv) being sometimes referred to herein as "disabling conduct"), (2) as to any
matter disposed of by settlement or a compromise payment by such Indemnitee,
pursuant to a consent decree or otherwise, no indemnification either for said
payment or for any other expenses shall be provided unless there has been a
determination that such settlement or compromise is in the best interests of the
Trust and that such Indemnitee appears to have acted in good faith in the
reasonable belief that such Indemnitee's action was in the best interest of the
Trust and did not involve disabling conduct by such Indemnitee and (3) with
respect to any


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action, suit or other proceeding voluntarily prosecuted by any Indemnitee as
plaintiff, indemnification shall be mandatory only if the prosecution of such
action, suit or other proceeding by such Indemnitee was authorized by a majority
of the full Board of Trustees of the Trust.

            (b) The Trust may make advance payments in connection with the
      expenses of defending any action with respect to which indemnification
      might be sought hereunder if the Trust receives a written affirmation of
      the Indemnitee's good faith belief that the standard of conduct necessary
      for indemnification has been met and a written undertaking to reimburse
      the Trust unless it is subsequently determined that such Indemnitee is
      entitled to such indemnification and if the Trustees of the Trust
      determine that the facts then known to them would not preclude
      indemnification. In addition, at least one of the following conditions
      must be met: (A) the Indemnitee shall provide security for such Indemnitee
      undertaking, (B) the Trust shall be insured against losses arising by
      reason of any unlawful advance, or (C) a majority of a quorum consisting
      of Trustees of the Trust who are neither "interested persons" of the Trust
      (as defined in Section 2(a)(19) of the 1940 Act) nor parties to the
      proceeding ("Disinterested Non Party Trustees") or an independent legal
      counsel in a written opinion, shall determine, based on a review of
      readily available facts (as opposed to a full trial type inquiry), that
      there is reason to believe that the Indemnitee ultimately will be found
      entitled to indemnification.

            (c) All determinations with respect to the standards for
      indemnification hereunder shall be made (1) by a final decision on the
      merits by a court or other body before whom the proceeding was brought
      that such Indemnitee is not liable or is not liable by reason of disabling
      conduct, or (2) in the absence of such a decision, by (i) a majority vote
      of a quorum of the Disinterested Non Party Trustees of the Trust, or (ii)
      if such a quorum is not obtainable or, even if obtainable, if a majority
      vote of such quorum so directs, independent legal counsel in a written
      opinion. All determinations that advance payments in connection with the
      expense of defending any proceeding shall be authorized and shall be made
      in accordance with the immediately preceding clause (2) above.

      The rights accruing to any Indemnitee under these provisions shall not
exclude any other right to which such Indemnitee may be lawfully entitled.

      11. Limitation on Liability. The Advisor will not be liable for any error
of judgment or mistake of law or for any loss suffered by the Advisor or by the
Trust in connection with the performance of this Agreement, except a loss
resulting from a breach of fiduciary duty with respect to the receipt of
compensation for services or a loss resulting from willful misfeasance, bad
faith or gross negligence on its part in the performance of its duties or from
reckless disregard by it of its duties under this Agreement. As used in this
paragraph 11, the term "Advisor" shall include any affiliates of the Advisor
performing services for the Trust contemplated hereby and partners, trustees,
officers and employees of the Advisor and of such affiliates.

      12. Duration and Termination. This Agreement shall become effective as of
the date hereof and, unless sooner terminated with respect to the Trust as
provided herein, shall continue in effect for a period of two years. Thereafter,
if not terminated, this Agreement shall continue in effect with respect to the
Trust for successive periods of 12 months, provided such continuance is


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specifically approved at least annually by both (a) the vote of a majority of
the Trust's Board of Trustees or the vote of a majority of the outstanding
voting securities of the Trust at the time outstanding and entitled to vote, and
(b) by the vote of a majority of the Trustees who are not parties to this
Agreement or interested persons of any party to this Agreement, cast in person
at a meeting called for the purpose of voting on such approval. Notwithstanding
the foregoing, this Agreement may be terminated by the Trust at any time,
without the payment of any penalty, upon giving the Advisor 60 days' notice
(which notice may be waived by the Advisor), provided that such termination by
the Trust shall be directed or approved by the vote of a majority of the
Trustees of the Trust in office at the time or by the vote of the holders of a
majority of the outstanding voting securities of the Trust entitled to vote, or
by the Advisor on 60 days' written notice (which notice may be waived by the
Trust). This Agreement will also immediately terminate in the event of its
assignment. (As used in this Agreement, the terms "majority of the outstanding
voting securities," "interested person" and "assignment" shall have the same
meanings of such terms in the 1940 Act.)

      13. Notices. Any notice under this Agreement shall be in writing to the
other party at such address as the other party may designate from time to time
for the receipt of such notice and shall be deemed to be received on the earlier
of the date actually received or on the fourth day after the postmark if such
notice is mailed first class postage prepaid.

      14. Amendment of this Agreement. This Agreement may be amended by the
parties only if such amendment is specifically approved by the vote of the Board
of Trustees of the Trust, including a majority of those Trustees who are not
parties to this Agreement or interested persons of any such party cast in person
at a meeting called for the purpose of voting on such approval and, where
required by the 1940 Act, by a vote of a majority of the outstanding voting
securities of the Trust.

      15. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of New York for contracts to be performed
entirely therein without reference to choice of law principles thereof and in
accordance with the applicable provisions of the 1940 Act. To the extent that
the applicable laws of the State of New York, or any of the provisions of this
Agreement, conflict with the applicable provisions of the 1940 Act, the latter
shall control.

      16. Miscellaneous. The captions in this Agreement are included for
convenience of reference only and in no way define or delimit any of the
provisions hereof or otherwise affect their construction or effect. If any
provision of this Agreement shall be held or made invalid by a court decision,
statute, rule or otherwise, the remainder of this Agreement shall not be
affected thereby. This Agreement shall be binding on, and shall inure to the
benefit of the parties hereto and their respective successors.

      17. Counterparts. This Agreement may be executed in counterparts by the
parties hereto, each of which shall constitute an original counterpart, and all
of which, together, shall constitute one Agreement.


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      IN WITNESS WHEREOF, the parties hereto have caused the foregoing
instrument to be executed by their duly authorized officers, all as of the day
and the year first above written.

                                     MASTER GOVERNMENT SECURITIES TRUST

                                     By: ___________________________________
                                         Name:  Donald C. Burke
                                         Title: Vice President

                                     BLACKROCK ADVISORS, LLC

                                     By: ___________________________________
                                         Name:  Donald C. Burke
                                         Title: Managing Director


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                                  Schedule A

                             Investment Advisory Fee

0.250% of the average daily Net Assets of the Trust not exceeding $500 million;
0.175% of the average daily Net Assets of the Trust exceeding $500 million but
not exceeding $1 billion; and 0.125% of the average daily Net Assets of the
Trust exceeding $1 billion