Exhibit (h)(20)

April 12, 2007

Barclays Global Investors Funds
Master Investment Portfolio
45 Fremont Street
San Francisco, California 94105

Expense Undertaking

Ladies and Gentlemen:

Reference is made to the Administration Agreement between Barclays Global
Investors Funds ("BGIF") and Barclays Global Investors, N.A. ("BGI") (the "BGIF
Administration Agreement") and the Administration Agreement between Master
Investment Portfolio ("MIP") and BGI (the "MIP Administration Agreement"),
pursuant to which BGI serves as Administrator for BGIF and MIP. In addition,
Barclays Global Fund Advisors ("BGFA") and MIP, on behalf of the series of MIP,
are parties to investment advisory agreements (the "Advisory Agreements"),
pursuant to which BGFA provides investment advisory services to such series and
receives compensation for such services at the rates set forth in the Advisory
Agreements (each, an "Advisory Fee").

Under the Administration Agreements, BGI is not required to bear the cost of
(1) the compensation of the Trustees who are not "interested persons" (as
defined in the Investment Company Act of 1940, as amended) of MIP or BGIF
("Independent Trustees"), (2) travel expenses of the Independent Trustees in
connection with their attendance at board and other meetings relating to MIP or
BGIF, as applicable, (3) fees and expenses of legal counsel for the Independent
Trustees, and (4) fees and expenses of the independent auditors of BGIF and MIP
(collectively, the "Independent Expenses").

Notwithstanding the BGIF Administration Agreement, BGI hereby agrees to
reimburse, or provide an offsetting credit against fees it is entitled to
receive from, BGIF in an amount equal to the Independent Expenses.

Notwithstanding the MIP Administration Agreement, for those series of MIP that
pay an administration fee to BGI under the MIP Administration Agreement, BGI
hereby agrees to reimburse, or provide an offsetting credit against fees it is
entitled to receive from, those series of MIP in an amount equal to the
Independent Expenses allocable to those series.

In addition, for those series of MIP that do not pay an administration fee to
BGI under the MIP Administration Agreement, BGFA agrees to cap the expenses of
such series at the rate at which those series of MIP pay an Advisory Fee to
BGFA.

This letter is effective as of January 1, 2007 and shall remain in effect until
April 30, 2009, unless earlier terminated by the written agreement of (a) MIP
and BGFA with



respect to MIP's Independent Expenses or (b) BGIF and BGI with respect to
BGIF's Independent Expenses.

Sincerely,

BARCLAYS GLOBAL INVESTORS, N.A.

By:    /s/ Raymund Santiago
       -------------------------
Name:  Raymund Santiago
Title: Principal

By:    /s/ Geoffrey Flynn
       -------------------------
Name:  Geoffrey Flynn
Title: Managing Director

BARCLAYS GLOBAL FUND ADVISORS

By:    /s/ Michael Latham
       -------------------------
Name:  Michael Latham
Title: Managing Director

By:    /s/ Steven Wong
       -------------------------
Name:  Steven Wong
Title: Principal