                             SECURITIES AND EXCHANGE COMMISSION  
                                     450 Fifth Street, NW
                                     Washington, DDC  20549

                        ------------------------------------------

                                          FORM 8-K
                                       CURRENT REPORT

                           Pursuant to Section 13 or 15(d) of the
                              Securities Exchange Act of 1934

                              For the Month of September, 2003

                WASHINGTON MUTUAL MSC MORTGAGE PASS-THROUGH CERTIFICATES,
                                     SERIES:  2003-ar4
                 (Exact name of the registrant as specified in charter)

                 Delaware              333-103345-19         94-2528990
               (State or other         (Commission          (IRS Employer
               jurisdiction of         File Number)         Identification
               Incorporation)                               Number)


                                   75 NORTH FAIRWAY DRIVE
                                   VERNON HILLS, IL  60061

                         (Address of principal executive offices)

                    Registrant's telephone number, including area code:

                                      (847) 549-6500



ITEM 5.C

     See Exhibit 99, the Distribution Report for the Month of September, 2003,
attached hereto.

ITEM 205497.

    FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION, AND EXHIBITS:


     EXHIBITS:

     99.   Washington Mutual MSC Mortgage Pass-Through Certificates,
          SERIES:  2003-ar4, Monthly Distribution Report for September 2003.

                                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 hereunto duly authorized.

Dated:    September 18, 2003

                                  WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
                                              (Registrant)

                                              By:   /s/
                                                    ------------------
                                                    BACC ALEXANDER
                                                    VICE PRESIDENT

FORM 8-K CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported):August 28, 2003

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

as Depositor and Master Servicer under a Pooling and Servicing Agreementdated as of August 1, 2003 providing for the issuance of

WASHINGTON MUTUAL MSC MORTGAGE PASS-THROUGH CERTIFICATES SERIES 2003-AR4 (Exact name of Registrant as specified in its charter)

Delaware		333-103345-19		94-2528990
(State or other jurisdiction of incorporation)		(Commission File Number)		(I.R.S. Employer Identification No.)

1201 THIRD AVENUE, WMT 1706 SEATTLE, WASHINGTON 98101 (Address of principal executive offices and Zip Code)

Registrant's telephone number, including area code: (206) 377-8555

ITEM 7. Financial Statements, Pro Forma Financial Information and Exhibits.

The following exhibit is filed herewith:

7.1 Pooling and Servicing Agreement by and among Washington Mutual Mortgage Securities Corp., as Depositor and Master Servicer, U.S. Bank National Association, as Trustee, and Christiana Bank & Trust Company, as Delaware Trustee, dated as of August 1, 2003.

The definition of Class C-Y Principal Reduction Amounts, included as Appendix 1 to the Pooling and Servicing Agreement, and the Mortgage Loan Schedule, included as Exhibit D to the Pooling and Servicing Agreement, have been intentionally omitted from this filing. Copies may be obtained from Washington Mutual Mortgage Securities Corp. or U.S. Bank National Association by contacting,

in the case of Washington Mutual Mortgage Securities Corp.,

Laura Kelsey Master Servicing Department Washington Mutual Mortgage Securities Corp. 75 N. Fairway Drive,VHF2A01 Vernon Hills, IL 60061 Telephone: (847) 393-5198 Facsimile: (847) 549-2997

in the case of U.S. Bank National Association,

Clare M. O'Brien Global Investor Services Group Corporate Trust U.S. Bank National Association One Federal Street, Third Floor Boston, MA 02111 Telephone: (617) 603-6402 Facsimile: (617) 603-6637

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 hereunto duly authorized.

		WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Date: September 12, 2003		By:		/s/ David H. Zielke David H. Zielke First Vice President and Counsel

Filing Compare · WASHINGTON MUTUAL MORT SEC CORP PASS THR CERT SE 2003-AR4