SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 8-K/A

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event

Reported): September 20, 2007

CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP. (as depositor under the Pooling and Servicing Agreement, relating to the Mortgage-Backed Pass-Through Certificates,

Series 2007-4)


CSMC MORTGAGE-BACKED TRUST SERIES 2007-4
(Exact name of Issuing Entity as specified in its charter)

CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
(Exact name of Depositor as specified in its charter)

DLJ MORTGAGE CAPITAL, INC.
(Exact name of Sponsor as specified in its charter)
CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
(Exact name of registrant as specified in its charter)
Delaware	333-135481	13-3320910
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(I.R.S. Employer Identification No.)

Eleven Madison Avenue New York, New York 10010
(Address of Principal Executive Offices) (Zip Code)

Registrant’s telephone number, including area code (212) 325-2000

Check the appropriate box below if the Form 8-K/A filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:


[ ]	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
[ ]	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
[ ]	Pre-commencement communications pursuant to Rule 14d-2(d) under the Exchange Act (17 CFR 240.14d-2(b))
[ ]	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 8.01. Other Events.

This Current Report on Form 8-K/A is being filed to amend and supplement the Current Report on Form 8-K originally dated June 14, 2007, in connection with the issuance of CSMC Mortgage-Backed Trust Series 2007-4, CSMC Mortgage-Backed Pass-Through Certificates, Series 2007-4, in order to correct certain errors contained in Exhibit 4.1 to such Form 8-K.

Item 9.01. Financial Statements and Exhibits.

(a) Financial statements of businesses acquired:

Not applicable.

(b) Pro forma financial information:

Not applicable.

(d) Exhibits:

Exhibit No.

Description

4.1

The Pooling and Servicing Agreement dated as of May 1, 2007, by and among the Depositor, the Seller, the Servicer, the Special Servicer, the Modification Oversight Agent, the Master Servicer, the Trust Administrator and the Trustee.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

CREDIT SUISSE FIRST BOSTON

MORTGAGE SECURITIES CORP.

By: /s/ Kevin Steele

Name: Kevin Steele

Title: Vice President

Dated: September 20, 2007

Exhibit Index

Exhibit

Page

4.1

MCKEE NELSON LLP

One Battery Park Plaza, 34 Floor

New York, New York 10004

Telephone: (917) 777-4200

Facsimile: (917) 777-4299

September 20, 2007

BY MODEM

Securities and Exchange Commission

Judiciary Plaza

450 Fifth Street, N.W.

Washington, D.C. 20549

Re:

Credit Suisse First Boston Mortgage Securities Corp.

CSMC Mortgage-Backed Trust Series 2007-4

Ladies and Gentlemen:

On behalf of Credit Suisse First Boston Mortgage Securities Corp (the “Company”), we enclose herewith for filing, pursuant to the Securities and Exchange Act of 1934, as amended, the Company’s Current Report on Form 8-K/A, for filing of the Pooling and Servicing Agreement in connection with the above-referenced transaction.

This Current Report on Form 8-K/A is being filed to amend and supplement the Current Report on Form 8-K originally dated June 14, 2007, in connection with the issuance of the Company’s CSMC Mortgage-Backed Trust Series 2007-4, CSMC Mortgage-Backed Pass-Through Certificates, Series 2007-4, in order to correct certain errors contained in Exhibit 4.1 to such Form 8-K.

Very truly yours,

_/s/ Ali Yenal

Ali Yenal

CSMC Trust 2007-4 8-K/A