ASSIGNMENT, ASSUMPTION AND RECOGNITION AGREEMENT

Exhibit 99.6a

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"), First National Bank of Nevada, as
seller (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 Master Mortgage
Loan Purchase and Warranties Agreement, dated as of January 20, 2005 (the
"January Purchase Agreement"), a certain First Amended and Restated Mortgage
Loan Purchase and Warranties Agreement, dated as of October 1, 2005 (the
"October Purchase Agreement"), and a certain Second Amended and Restated
Mortgage Loan Purchase and Warranties Agreement, dated as of April 1, 2006
(the "April Purchase Agreement" and together with the January Purchase
Agreement and the October Purchase Agreement, the "Purchase Agreements"),
pursuant to which MSMCI has acquired certain Mortgage Loans;

WHEREAS, in connection with the transfer of the Mortgage Loans
hereunder, the Seller agrees that, from and after the date hereof, each
Mortgage Loan transferred hereunder will be subject to the October Purchase
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 Purchase
Agreements 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 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 Purchase Agreements 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
Purchase Agreements which are not the Specified Mortgage Loans.

(b) On and 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

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provided under the Purchase Agreements 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 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 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 Purchase Agreements. Accordingly, the right of MSMCI to consent to any
amendment of the Purchase Agreements and its rights concerning waivers as set
forth in Section 22 of the October Purchase Agreement shall be exercisable, to
the extent any such amendment or waiver affects the Specified Mortgage Loans
or any of the rights under the Purchase Agreements with respect thereto,
solely by the Trustee as assignee of MSMCI.

(c) It is expressly understood and agreed by the parties hereto that (i)
this Assignment is executed and delivered by LaSalle Bank National
Association, not individually or personally but solely on behalf of the Trust,
as the Assignee, in the exercise of the powers and authority conferred and
vested in it, as Trustee, pursuant to the Pooling and Servicing Agreement
dated as of the date hereof (the "Pooling and Servicing Agreement") among the
Depositor, Wells Fargo Bank, National Association, as securities administrator
(the "Securities Administrator") and master servicer (the "Master Servicer"),
and the Trustee, (ii) each of the representations, undertakings