ASSIGNMENT, ASSUMPTION AND RECOGNITION AGREEMENT

Exhibit 99.11a

EXECUTION COPY

ASSIGNMENT, ASSUMPTION AND RECOGNITION AGREEMENT

THIS ASSIGNMENT, ASSUMPTION AND RECOGNITION AGREEMENT (this "Assignment"),
dated as of September 1, 2006, is entered into among Morgan Stanley Capital I
Inc., a Delaware corporation (the "Depositor"), Morgan Stanley Mortgage Capital
Inc. ("MSMCI"), Wachovia Mortgage Corporation as seller ("Wachovia," or the
"Seller"), and acknowledged by LaSalle Bank National Association, as trustee
(the "Trustee") of Morgan Stanley Mortgage Loan Trust 2006-13ARX (the "Trust").

RECITALS

WHEREAS MSMCI and the Seller have entered into a certain Seller's
Purchase, Warranties and Interim Servicing Agreement, dated as of February 28,
2005 (as amended or modified to the date hereof, the "Agreement"), pursuant to
which MSMCI has acquired certain Mortgage Loans pursuant to the terms of the
Agreement;

WHEREAS the Depositor has agreed, on the terms and conditions contained
herein, to purchase from MSMCI certain of the Mortgage Loans (the "Specified
Mortgage Loans") which are subject to the provisions of the Agreement and are
listed on the mortgage loan schedule attached as Exhibit I hereto (the
"Specified Mortgage Loan Schedule"); and

WHEREAS the Trustee, on behalf of the Trust, has agreed, on the terms and
conditions contained herein, to purchase from the Depositor the Specified
Mortgage Loans;

NOW, THEREFORE, in consideration of the mutual promises contained herein
and other good and valuable consideration (the receipt and sufficiency of which
are hereby acknowledged), the parties agree as follows:

1. Assignment and Assumption

(a) On and as of the date hereof, MSMCI hereby sells, assigns and
transfers to the Depositor all of its right, title and interest in the Specified
Mortgage Loans and all rights and obligations related thereto as provided under
the Agreement to the extent relating to the Specified Mortgage Loans, the
Depositor hereby accepts such assignment from MSMCI (the "First Assignment and
Assumption"), and the Seller hereby acknowledges the First Assignment and
Assumption.

MSMCI specifically reserves and does not assign to the Depositor
hereunder any and all right, title and interest in, to and under and all
obligations of MSMCI with respect to any Mortgage Loans subject to the Agreement
which are not the Specified Mortgage Loans.

(b) On and as of the date hereof, immediately after giving effect to the
First Assignment and Assumption, the Depositor hereby sells, assigns and
transfers to the Trustee, on behalf of the Trust, all of its right, title and
interest in the Specified Mortgage Loans and all rights and obligations related
thereto as provided under the Agreement to the extent relating to the Specified
Mortgage Loans, and the Trustee, on behalf of the Trust, hereby accepts such
assignment from the Depositor (the "Second Assignment and Assumption"), and the
Seller hereby acknowledges the Second Assignment and Assumption.

(c) On and as of the date hereof, MSMCI represents and warrants to the
Depositor and the Trustee that MSMCI has not taken any action that would serve
to impair or encumber the respective


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ownership interests of the Depositor and the Trustee in the Specified
Mortgage Loans since the date of MSMCI's acquisition of the Specified Mortgage
Loans.

2. Recognition of Trustee

(a) From and after the date hereof, both MSMCI and the Seller shall note
the transfer of the Specified Mortgage Loans to the Trustee, in their respective
books and records and shall recognize the Trustee, on behalf of the Trust, as of
the date hereof, as the owner of the Specified Mortgage Loans. It is the
intention of the Seller, the Servicer, the Depositor, the Trustee and MSMCI that
this Assignment shall be binding upon and inure to the benefit of the Depositor,
the Trustee and MSMCI and their respective successors and assigns.

(b) Without in any way limiting the foregoing, the parties confirm that
this Assignment includes the rights relating to amendments or waivers under the
Agreement. Accordingly, the right of MSMCI to consent to any amendment of the
Agreement and its rights concerning waivers as set forth in Sections 11.02 and
8.02 of the Agreement shall be exercisable, to the extent any such amendment or
waiver affects the Specified Mortgage Loans or any of the rights under the
Agreement with respect theret