Exhibit 4(a)

                         INVESTMENT MANAGEMENT AGREEMENT

      AGREEMENT, dated September 29, 2006, between BlackRock Master Trust (the
"Trust"), a Delaware statutory trust, on behalf of BlackRock Master
International Portfolio (the "Fund") and BlackRock Advisors, LLC, a Delaware
limited liability company (the "Advisor").

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

      WHEREAS, the Board of Trustees of the Trust has established and designated
the Fund as a series of the Trust; and

      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.

      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 Fund with respect to the investment of the
Fund's assets and to supervise and arrange for the day to day operations of the
Fund and the purchase of securities for and the sale of securities held in the
investment portfolio of the Fund.

      2. Duties and Obligations of the Advisor with Respect to Investment of
Assets of the Fund. 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 Fund's assets and in connection therewith
have complete discretion in purchasing and selling securities and other assets
for the Fund and in voting, exercising consents and exercising all other rights
appertaining to such securities and other assets on behalf of the Fund; (ii)
supervise continuously the investment program of the Fund 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 Fund; and (iv) provide investment research to the
Fund.

      3. Duties and Obligations of Advisor with Respect to the Administration of
the Fund. 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 Fund's Custodian, Transfer Agent and Dividend Disbursing
Agent and other service providers) for the Fund. To the extent requested by the
Fund, the Advisor agrees to provide the following administrative services:

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

<PAGE>

            (b) Oversee the maintenance by the Fund's Custodian and Transfer
Agent and Dividend Disbursing Agent of certain books and records of the Fund as
required under Rule 31a1(b)(4) of the 1940 Act and maintain (or oversee
maintenance by such other persons as approved by the Board of Trustees) such
other books and records required by law or for the proper operation of the Fund;

            (c) Oversee the preparation and filing of the Fund'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
Fund's expenses;

            (e) Prepare for review and approval by officers of the Trust's
financial information for the Fund's semiannual and annual reports, proxy
statements and other communications with shareholders required or otherwise to
be sent to Fund 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 Fund'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
Fund as may be mutually agreed upon and not otherwise appropriately prepared by
the Fund'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 Fund'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 Fund's
service providers;

            (k) Oversee the Fund'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 Fund and monitor financial
and shareholder accounting services;

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


                                       2
<PAGE>

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

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

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

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

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

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

      The Fund 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 Fund will reimburse
the Advisor and its affiliates for their costs in providing accounting services
to the Fund.

      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 Fund as set forth in its 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 and

            (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 Fund 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


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<PAGE>

      determines in good faith that such commission is reasonable in terms
      either of the transaction or the overall responsibility of the Advisor to
      the Fund and its other clients and that the total commissions paid by the
      Fund will be reasonable in relation to the benefits to the Fund 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 Fund, its investment advisory personnel will not
      inquire or take into consideration whether the issuer of securities
      proposed for purchase or sale for the Fund's account are customers of the
      commercial department of its affiliates; and

            (iii) treat confidentially and as proprietary information of the
      Fund all records and other information relative to the Fund, and the
      Fund'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 Fund, 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 Fund.

      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 Fund. 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


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<PAGE>

shall bear the costs of any salaries or trustees' fees of any officers or
trustees of the Trust who 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 Fund 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 Fund operations or the operations of
other investment companies advised by the Advisor.

      9. Compensation of the Advisor. (a) The Trust, on behalf of the Fund,
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 Fund's Net
Assets. "Net Assets" means the total assets of the Fund 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 Fund shall be
calculated pursuant to the procedures adopted by resolutions of the Trustees of
the Trust for calculating the value of the Fund's assets or delegating such
calculations to third parties.

            10. Indemnity. (a) The Fund may, in the discretion of the Board of
Trustees of the Trust, indemnify the Advisor, and each of the Advisor's
directors, officers, employees, agents, associates and controlling persons and
the directors, 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 the Fund 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 Fund and that such Indemnitee


                                       5
<PAGE>

appears to have acted in good faith in the reasonable belief that such
Indemnitee's action was in the best interest of the Fund and did not involve
disabling conduct by such Indemnitee and (3) with respect to any 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 Fund 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 Fund 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
Fund 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
Section 11, the term "Advisor" shall include any affiliates of the Advisor
performing services for the Fund contemplated hereby and partners, directors,
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 Fund as
provided herein, shall continue in effect for a period of two years. Thereafter,
if not terminated, this Agreement shall continue in


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<PAGE>

effect with respect to the Fund for successive periods of 12 months, provided
such continuance is 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 Fund 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, on
behalf of the Fund, 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, on behalf of the Fund, 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 voting
securities of the Fund at the time outstanding and entitled to vote, or by the
Advisor on 60 days' written notice (which notice may be waived by the Trust, on
behalf of the Fund). 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 Fund.

      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, conflict
with the applicable provisions of the 1940 Act, the latter shall control.

      16. Use of the Name BlackRock. The Advisor has consented to the use by the
Trust of the name or identifying word "BlackRock" in the name of the Trust and
the Fund. Such consent is conditioned upon the employment of the Advisor as the
investment advisor to the Fund. The name or identifying word "BlackRock" may be
used from time to time in other connections and for other purposes by the
Advisor and any of its affiliates. The Advisor may require the Trust and the
Fund to cease using "BlackRock" in the name of the Trust and the Fund if the
Fund ceases to employ, for any reason, the Advisor, any successor thereto or any
affiliate thereof as investment advisor of the Fund.

      17. 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


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<PAGE>

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.

      18. 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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<PAGE>

      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.

                                        BLACKROCK MASTER TRUST, on behalf of its
                                        series, BLACKROCK MASTER INTERNATIONAL
                                        PORTFOLIO

                                        By: ____________________________________
                                        Name:  Donald C. Burke
                                        Title: Vice President & Treasurer

                                        BLACKROCK ADVISORS, LLC

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


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<PAGE>

                                   Schedule A

                             Investment Advisory Fee

<TABLE>
<CAPTION>
Portion of Average Daily Value of Net Assets of the Fund                      Investment Advisory Fee
--------------------------------------------------------                      -----------------------
<S>                                                                                    <C>
Not exceeding $500 million...................................................          0.75%

In excess of $500 million....................................................          0.70%
</TABLE>