WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 09/25/2003

Class	Cusip	Orig Prin Bal	Begin Prin Bal	Int Rate Accrued	Int Rate Paid	Int Dist	Prin Dist	Int Shortfall	Prin Loss	Deferred Interest	Int Reimbursed	Unscheduled Int	Prin Reimbursed	Total Dist	Ending Class Bal
IA	939336J20	$114,560,800.00	$114,560,800.00	4.6137135146%	4.6137135146%	$440,458.93	$2,534,438.07	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$2,974,896.99	$112,026,361.93
IIA1	939336J38	$29,038,500.00	$29,038,500.00	4.2001409732%	4.2001409732%	$101,638.16	$186,793.32	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$288,431.48	$28,851,706.68
IIA2	939336L27	$356,021,800.00	$356,021,800.00	4.2341409732%	4.2341409732%	$1,256,205.41	$2,290,149.04	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$3,546,354.45	$353,731,650.96
IIIA	939336J53	$60,312,800.00	$60,312,800.00	4.6142077297%	4.6142077297%	$231,913.16	$15,924.14	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$247,837.29	$60,296,875.86
IVA	939336J61	$145,516,900.00	$145,516,900.00	4.9707616616%	4.9707616616%	$602,774.86	$297,507.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$900,281.86	$145,219,393.00
VA	939336J79	$17,753,300.00	$17,753,300.00	4.3194983445%	4.3194983445%	$63,904.46	$6,182.78	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$70,087.24	$17,747,117.22
VIA	939336J87	$49,402,200.00	$49,402,200.00	4.6705162046%	4.6705162046%	$192,278.15	$8,787.48	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$201,065.63	$49,393,412.52
VIIA	939336J95	$50,326,600.00	$50,326,600.00	4.3834889789%	4.3834889789%	$183,838.41	$11,685.69	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$195,524.11	$50,314,914.31
IIX	939336J95	$385,060,300.00	$385,060,300.00	0.6135640374%	0.6135640374%	$196,882.63	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$196,882.63	$382,583,357.64
M	939336K28	$34,746,000.00	$34,746,000.00	4.7681564102%	4.7681564102%	$138,061.97	$6,977.36	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$145,039.33	$34,739,022.64
B1	939336K36	$20,116,100.00	$20,116,100.00	4.7681564102%	4.7681564102%	$79,930.59	$4,039.52	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$83,970.12	$20,112,060.48
B2	939336K44	$9,143,800.00	$9,143,800.00	4.7681564102%	4.7681564102%	$36,332.56	$1,836.17	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$38,168.73	$9,141,963.83
B3	939336K51	$9,143,600.00	$9,143,600.00	4.7681564102%	4.7681564102%	$36,331.76	$1,836.13	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$38,167.89	$9,141,763.87
B4	939336K77	$11,886,800.00	$11,886,800.00	4.7681564102%	4.7681564102%	$47,231.77	$2,386.99	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$49,618.76	$11,884,413.01
B5	939336K85	$3,200,300.00	$3,200,300.00	4.7681564102%	4.7681564102%	$12,716.28	$642.65	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$13,358.93	$3,199,657.35
B6	939336K93	$3,200,693.47	$3,200,693.47	4.7681564102%	4.7681564102%	$12,717.84	$642.73	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$13,360.57	$3,200,050.74
R	939336K69	$100.00	$100.00	4.6140000000%	10.4550232985%	$0.87	$100.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$100.87	$0.00
R_SYN	XXXXXXXXX	$0.00	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
Total		$914,370,293.47	$914,370,293.47			$3,633,217.79	$5,369,929.09	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$9,003,146.88	$909,000,364.38

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 09/25/2003

Class	Orig Face	Beg Bal	Prin Loss	Deferred Interest	Total Prin	End Cert Pct	End Cert Bal
IA	$114,560,800.00	$114,560,800.00	$0.00	$0.00	$2,534,438.07	0.9778769171	$112,026,361.93
IIA1	$29,038,500.00	$29,038,500.00	$0.00	$0.00	$186,793.32	0.9935673909	$28,851,706.68
IIA2	$356,021,800.00	$356,021,800.00	$0.00	$0.00	$2,290,149.04	0.9935673910	$353,731,650.96
IIIA	$60,312,800.00	$60,312,800.00	$0.00	$0.00	$15,924.14	0.9997359741	$60,296,875.86
IVA	$145,516,900.00	$145,516,900.00	$0.00	$0.00	$297,507.00	0.9979555158	$145,219,393.00
VA	$17,753,300.00	$17,753,300.00	$0.00	$0.00	$6,182.78	0.9996517391	$17,747,117.22
VIA	$49,402,200.00	$49,402,200.00	$0.00	$0.00	$8,787.48	0.9998221237	$49,393,412.52
VIIA	$50,326,600.00	$50,326,600.00	$0.00	$0.00	$11,685.69	0.9997678029	$50,314,914.31
IIX	$385,060,300.00	$385,060,300.00	$0.00	$0.00	$0.00	0.9935673910	$382,583,357.64
M	$34,746,000.00	$34,746,000.00	$0.00	$0.00	$6,977.36	0.9997991895	$34,739,022.64
B1	$20,116,100.00	$20,116,100.00	$0.00	$0.00	$4,039.52	0.9997991897	$20,112,060.48
B2	$9,143,800.00	$9,143,800.00	$0.00	$0.00	$1,836.17	0.9997991896	$9,141,963.83
B3	$9,143,600.00	$9,143,600.00	$0.00	$0.00	$1,836.13	0.9997991896	$9,141,763.87
B4	$11,886,800.00	$11,886,800.00	$0.00	$0.00	$2,386.99	0.9997991899	$11,884,413.01
B5	$3,200,300.00	$3,200,300.00	$0.00	$0.00	$642.65	0.9997991907	$3,199,657.35
B6	$3,200,693.47	$3,200,693.47	$0.00	$0.00	$642.73	0.9997991904	$3,200,050.74
R	$100.00	$100.00	$0.00	$0.00	$100.00	0.0000000000	$0.00
R_SYN	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
Total	$914,370,293.47	$914,370,293.47	$0.00	$0.00	$5,369,929.09	0.9941271833	$909,000,364.38

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 09/25/2003
PER $1000 DENOMINATION
Class	Orig Face	Beg Bal	Prin Loss	Deferred Interest	Total Prin	End Cert Pct	End Cert Bal
IA	$114,560,800.00	1,000.00000000	0.00000000	0.00000000	22.12308285	0.9778769171	977.87691715
IIA1	$29,038,500.00	1,000.00000000	0.00000000	0.00000000	6.43260912	0.9935673909	993.56739088
IIA2	$356,021,800.00	1,000.00000000	0.00000000	0.00000000	6.43260901	0.9935673910	993.56739099
IIIA	$60,312,800.00	1,000.00000000	0.00000000	0.00000000	0.26402588	0.9997359741	999.73597412
IVA	$145,516,900.00	1,000.00000000	0.00000000	0.00000000	2.04448418	0.9979555158	997.95551582
VA	$17,753,300.00	1,000.00000000	0.00000000	0.00000000	0.34826089	0.9996517391	999.65173911
VIA	$49,402,200.00	1,000.00000000	0.00000000	0.00000000	0.17787629	0.9998221237	999.82212371
VIIA	$50,326,600.00	1,000.00000000	0.00000000	0.00000000	0.23219709	0.9997678029	999.76780291
IIX	$385,060,300.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.9935673910	993.56739098
M	$34,746,000.00	1,000.00000000	0.00000000	0.00000000	0.20081045	0.9997991895	999.79918955
B1	$20,116,100.00	1,000.00000000	0.00000000	0.00000000	0.20081030	0.9997991897	999.79918970
B2	$9,143,800.00	1,000.00000000	0.00000000	0.00000000	0.20081039	0.9997991896	999.79918961
B3	$9,143,600.00	1,000.00000000	0.00000000	0.00000000	0.20081040	0.9997991896	999.79918960
B4	$11,886,800.00	1,000.00000000	0.00000000	0.00000000	0.20081014	0.9997991899	999.79918986
B5	$3,200,300.00	1,000.00000000	0.00000000	0.00000000	0.20080930	0.9997991907	999.79919070
B6	$3,200,693.47	1,000.00000000	0.00000000	0.00000000	0.20080961	0.9997991904	999.79919039
R	$100.00	1,000.00000000	0.00000000	0.00000000	1000.00000000	0.0000000000	0.00000000
R_SYN	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 09/25/2003

Class	Orig Face	Int Rate Accrued	Int Rate Paid	Beg Cert Prin/Not Bal	Curent Int Accrued	Int Shortfall	Unscheduled Int	Int Reimbursed	Total Int Dist
IA	$114,560,800.00	4.6137135146%	4.6137135146%	$114,560,800.00	$440,458.93	$0.00	$0.00	$0.00	$440,458.93
IIA1	$29,038,500.00	4.2001409732%	4.2001409732%	$29,038,500.00	$101,638.16	$0.00	$0.00	$0.00	$101,638.16
IIA2	$356,021,800.00	4.2341409732%	4.2341409732%	$356,021,800.00	$1,256,205.41	$0.00	$0.00	$0.00	$1,256,205.41
IIIA	$60,312,800.00	4.6142077297%	4.6142077297%	$60,312,800.00	$231,913.16	$0.00	$0.00	$0.00	$231,913.16
IVA	$145,516,900.00	4.9707616616%	4.9707616616%	$145,516,900.00	$602,774.86	$0.00	$0.00	$0.00	$602,774.86
VA	$17,753,300.00	4.3194983445%	4.3194983445%	$17,753,300.00	$63,904.46	$0.00	$0.00	$0.00	$63,904.46
VIA	$49,402,200.00	4.6705162046%	4.6705162046%	$49,402,200.00	$192,278.15	$0.00	$0.00	$0.00	$192,278.15
VIIA	$50,326,600.00	4.3834889789%	4.3834889789%	$50,326,600.00	$183,838.41	$0.00	$0.00	$0.00	$183,838.41
IIX	$385,060,300.00	0.6135640374%	0.6135640374%	$385,060,300.00	$196,882.63	$0.00	$0.00	$0.00	$196,882.63
M	$34,746,000.00	4.7681564102%	4.7681564102%	$34,746,000.00	$138,061.97	$0.00	$0.00	$0.00	$138,061.97
B1	$20,116,100.00	4.7681564102%	4.7681564102%	$20,116,100.00	$79,930.59	$0.00	$0.00	$0.00	$79,930.59
B2	$9,143,800.00	4.7681564102%	4.7681564102%	$9,143,800.00	$36,332.56	$0.00	$0.00	$0.00	$36,332.56
B3	$9,143,600.00	4.7681564102%	4.7681564102%	$9,143,600.00	$36,331.76	$0.00	$0.00	$0.00	$36,331.76
B4	$11,886,800.00	4.7681564102%	4.7681564102%	$11,886,800.00	$47,231.77	$0.00	$0.00	$0.00	$47,231.77
B5	$3,200,300.00	4.7681564102%	4.7681564102%	$3,200,300.00	$12,716.28	$0.00	$0.00	$0.00	$12,716.28
B6	$3,200,693.47	4.7681564102%	4.7681564102%	$3,200,693.47	$12,717.84	$0.00	$0.00	$0.00	$12,717.84
R	$100.00	4.6140000000%	10.4550232985%	$100.00	$0.87	$0.00	$0.00	$0.00	$0.87
R_SYN	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
Total	$914,370,293.47			$914,370,293.47	$3,633,217.79	$0.00	$0.00	$0.00	$3,633,217.79

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 09/25/2003
PER $1000 DENOMINATION
Class	Orig Face	Int Rate Accrued	Int Rate Paid	Beg Cert Prin/Not Bal	Curent Int Accrued	Int Shortfall	Unscheduled Int	Int Reimbursed	Total Int Dist
IA	$114,560,800.00	4.6137135146%	4.6137135146%	1,000.00000000	3.84476130	0.00000000	0.00000000	0.00000000	3.84476130
IIA1	$29,038,500.00	4.2001409732%	4.2001409732%	1,000.00000000	3.50011743	0.00000000	0.00000000	0.00000000	3.50011743
IIA2	$356,021,800.00	4.2341409732%	4.2341409732%	1,000.00000000	3.52845081	0.00000000	0.00000000	0.00000000	3.52845081
IIIA	$60,312,800.00	4.6142077297%	4.6142077297%	1,000.00000000	3.84517316	0.00000000	0.00000000	0.00000000	3.84517316
IVA	$145,516,900.00	4.9707616616%	4.9707616616%	1,000.00000000	4.14230141	0.00000000	0.00000000	0.00000000	4.14230141
VA	$17,753,300.00	4.3194983445%	4.3194983445%	1,000.00000000	3.59958205	0.00000000	0.00000000	0.00000000	3.59958205
VIA	$49,402,200.00	4.6705162046%	4.6705162046%	1,000.00000000	3.89209691	0.00000000	0.00000000	0.00000000	3.89209691
VIIA	$50,326,600.00	4.3834889789%	4.3834889789%	1,000.00000000	3.65290741	0.00000000	0.00000000	0.00000000	3.65290741
IIX	$385,060,300.00	0.6135640374%	0.6135640374%	1,000.00000000	0.51130337	0.00000000	0.00000000	0.00000000	0.51130337
M	$34,746,000.00	4.7681564102%	4.7681564102%	1,000.00000000	3.97346371	0.00000000	0.00000000	0.00000000	3.97346371
B1	$20,116,100.00	4.7681564102%	4.7681564102%	1,000.00000000	3.97346354	0.00000000	0.00000000	0.00000000	3.97346354
B2	$9,143,800.00	4.7681564102%	4.7681564102%	1,000.00000000	3.97346399	0.00000000	0.00000000	0.00000000	3.97346399
B3	$9,143,600.00	4.7681564102%	4.7681564102%	1,000.00000000	3.97346341	0.00000000	0.00000000	0.00000000	3.97346341
B4	$11,886,800.00	4.7681564102%	4.7681564102%	1,000.00000000	3.97346384	0.00000000	0.00000000	0.00000000	3.97346384
B5	$3,200,300.00	4.7681564102%	4.7681564102%	1,000.00000000	3.97346499	0.00000000	0.00000000	0.00000000	3.97346499
B6	$3,200,693.47	4.7681564102%	4.7681564102%	1,000.00000000	3.97346391	0.00000000	0.00000000	0.00000000	3.97346391
R	$100.00	4.6140000000%	10.4550232985%	1,000.00000000	8.70000000	0.00000000	0.00000000	0.00000000	8.70000000
R_SYN	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4 WEIGHTED AVERAGE PC RATE: 4.76816%
POOL NUMBER: Group 1(2180,2181,2182,2183,2184,2185,2186)
ISSUE DATE: 08/29/2003
CERTIFICATE BALANCE AT ISSUE: $914,370,293.51
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	2659		$914,370,293.51
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$183,615.12
Unscheduled Principal Collection/Reversals		$63,788.57
Liquidations-in-full	9	$5,122,525.40
Net principal Distributed		$5,369,929.09	-$5,369,929.09

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	2650		$909,000,364.42

SCHEDULED INTEREST AT MORTGAGE RATE:		$3,938,007.73

UNSCHEDULED INTEREST AT MORTGAGE RATE:
Unscheduled Interest Collection/Reversals		$0.00
Interest Uncollected on Liquidation		$0.00
Interest Uncollected on Non-Earning Assets		$0.00
Net Unscheduled Interest Distributed		$0.00

OTHER:
Loan Conversion Fees		$0.00
Expense Reimbursements		$0.00
Gain on Liquidations		$0.00
Hazard Insurance Premium Refunds		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$304,789.94

UNSCHEDULED SERVICING FEES:
Unscheduled Service Fee Collections/Reversals		$0.00
Servicing Fees Uncollected on Liquidation		$0.00
Servicing Fees Uncollected/Non-Earning Assets		$0.00
Net Unscheduled Service Fees Distributed		$0.00

MISCELLANEOUS EXPENSES:		$0.00

NET FUNDS DISTRIBUTED:		$9,003,146.88

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4 WEIGHTED AVERAGE PC RATE: 4.61371%
POOL NUMBER: 2180
ISSUE DATE: 08/29/2003
CERTIFICATE BALANCE AT ISSUE: $127,289,895.54
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	252		$127,289,895.54
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$25,574.53
Unscheduled Principal Collection/Reversals		$2,092.97
Liquidations-in-full	4	$2,509,428.02
Net principal Distributed		$2,537,095.52	-$2,537,095.52

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	248		$124,752,800.02

SCHEDULED INTEREST AT MORTGAGE RATE:		$531,829.24

UNSCHEDULED INTEREST AT MORTGAGE RATE:
Unscheduled Interest Collection/Reversals		$0.00
Interest Uncollected on Liquidation		$0.00
Interest Uncollected on Non-Earning Assets		$0.00
Net Unscheduled Interest Distributed		$0.00

OTHER:
Loan Conversion Fees		$0.00
Expense Reimbursements		$0.00
Gain on Liquidations		$0.00
Hazard Insurance Premium Refunds		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$42,429.94

UNSCHEDULED SERVICING FEES:
Unscheduled Service Fee Collections/Reversals		$0.00
Servicing Fees Uncollected on Liquidation		$0.00
Servicing Fees Uncollected/Non-Earning Assets		$0.00
Net Unscheduled Service Fees Distributed		$0.00

MISCELLANEOUS EXPENSES:		$0.00

NET FUNDS DISTRIBUTED:		$3,026,494.82

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4 WEIGHTED AVERAGE PC RATE: 4.84514%
POOL NUMBER: 2181
ISSUE DATE: 08/29/2003
CERTIFICATE BALANCE AT ISSUE: $427,844,880.53
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	852		$427,844,880.53
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$77,699.27
Unscheduled Principal Collection/Reversals		$54,213.03
Liquidations-in-full	4	$2,352,800.00
Net principal Distributed		$2,484,712.30	-$2,484,712.30

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	848		$425,360,168.23

SCHEDULED INTEREST AT MORTGAGE RATE:		$1,870,088.97

UNSCHEDULED INTEREST AT MORTGAGE RATE:
Unscheduled Interest Collection/Reversals		$0.00
Interest Uncollected on Liquidation		$0.00
Interest Uncollected on Non-Earning Assets		$0.00
Net Unscheduled Interest Distributed		$0.00

OTHER:
Loan Conversion Fees		$0.00
Expense Reimbursements		$0.00
Gain on Liquidations		$0.00
Hazard Insurance Premium Refunds		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$142,614.95

UNSCHEDULED SERVICING FEES:
Unscheduled Service Fee Collections/Reversals		$0.00
Servicing Fees Uncollected on Liquidation		$0.00
Servicing Fees Uncollected/Non-Earning Assets		$0.00
Net Unscheduled Service Fees Distributed		$0.00

MISCELLANEOUS EXPENSES:		$0.00

NET FUNDS DISTRIBUTED:		$4,212,186.32

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4 WEIGHTED AVERAGE PC RATE: 4.61421%
POOL NUMBER: 2182
ISSUE DATE: 08/29/2003
CERTIFICATE BALANCE AT ISSUE: $67,014,291.78
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	334		$67,014,291.78
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$16,513.18
Unscheduled Principal Collection/Reversals		$1,062.29
Liquidations-in-full	0	$0.00
Net principal Distributed		$17,575.47	-$17,575.47

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	334		$66,996,716.31

SCHEDULED INTEREST AT MORTGAGE RATE:		$280,019.70

UNSCHEDULED INTEREST AT MORTGAGE RATE:
Unscheduled Interest Collection/Reversals		$0.00
Interest Uncollected on Liquidation		$0.00
Interest Uncollected on Non-Earning Assets		$0.00
Net Unscheduled Interest Distributed		$0.00

OTHER:
Loan Conversion Fees		$0.00
Expense Reimbursements		$0.00
Gain on Liquidations		$0.00
Hazard Insurance Premium Refunds		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$22,338.05

UNSCHEDULED SERVICING FEES:
Unscheduled Service Fee Collections/Reversals		$0.00
Servicing Fees Uncollected on Liquidation		$0.00
Servicing Fees Uncollected/Non-Earning Assets		$0.00
Net Unscheduled Service Fees Distributed		$0.00

MISCELLANEOUS EXPENSES:		$0.00

NET FUNDS DISTRIBUTED:		$275,257.12

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4 WEIGHTED AVERAGE PC RATE: 4.97076%
POOL NUMBER: 2183
ISSUE DATE: 08/29/2003
CERTIFICATE BALANCE AT ISSUE: $161,685,471.62
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	768		$161,685,471.62
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$36,576.81
Unscheduled Principal Collection/Reversals		$4,290.50
Liquidations-in-full	1	$260,297.38
Net principal Distributed		$301,164.69	-$301,164.69

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	767		$161,384,306.93

SCHEDULED INTEREST AT MORTGAGE RATE:		$723,645.21

UNSCHEDULED INTEREST AT MORTGAGE RATE:
Unscheduled Interest Collection/Reversals		$0.00
Interest Uncollected on Liquidation		$0.00
Interest Uncollected on Non-Earning Assets		$0.00
Net Unscheduled Interest Distributed		$0.00

OTHER:
Loan Conversion Fees		$0.00
Expense Reimbursements		$0.00
Gain on Liquidations		$0.00
Hazard Insurance Premium Refunds		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$53,895.05

UNSCHEDULED SERVICING FEES:
Unscheduled Service Fee Collections/Reversals		$0.00
Servicing Fees Uncollected on Liquidation		$0.00
Servicing Fees Uncollected/Non-Earning Assets		$0.00
Net Unscheduled Service Fees Distributed		$0.00

MISCELLANEOUS EXPENSES:		$0.00

NET FUNDS DISTRIBUTED:		$970,914.85

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4 WEIGHTED AVERAGE PC RATE: 4.31950%
POOL NUMBER: 2184
ISSUE DATE: 08/29/2003
CERTIFICATE BALANCE AT ISSUE: $19,725,894.94
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	92		$19,725,894.94
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$5,578.74
Unscheduled Principal Collection/Reversals		$1,161.92
Liquidations-in-full	0	$0.00
Net principal Distributed		$6,740.66	-$6,740.66

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	92		$19,719,154.28

SCHEDULED INTEREST AT MORTGAGE RATE:		$77,580.29

UNSCHEDULED INTEREST AT MORTGAGE RATE:
Unscheduled Interest Collection/Reversals		$0.00
Interest Uncollected on Liquidation		$0.00
Interest Uncollected on Non-Earning Assets		$0.00
Net Unscheduled Interest Distributed		$0.00

OTHER:
Loan Conversion Fees		$0.00
Expense Reimbursements		$0.00
Gain on Liquidations		$0.00
Hazard Insurance Premium Refunds		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$6,575.27

UNSCHEDULED SERVICING FEES:
Unscheduled Service Fee Collections/Reversals		$0.00
Servicing Fees Uncollected on Liquidation		$0.00
Servicing Fees Uncollected/Non-Earning Assets		$0.00
Net Unscheduled Service Fees Distributed		$0.00

MISCELLANEOUS EXPENSES:		$0.00

NET FUNDS DISTRIBUTED:		$77,745.68

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4 WEIGHTED AVERAGE PC RATE: 4.67052%
POOL NUMBER: 2185
ISSUE DATE: 08/29/2003
CERTIFICATE BALANCE AT ISSUE: $54,891,373.23
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	250		$54,891,373.23
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$8,869.10
Unscheduled Principal Collection/Reversals		$805.30
Liquidations-in-full	0	$0.00
Net principal Distributed		$9,674.40	-$9,674.40

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	250		$54,881,698.83

SCHEDULED INTEREST AT MORTGAGE RATE:		$231,939.71

UNSCHEDULED INTEREST AT MORTGAGE RATE:
Unscheduled Interest Collection/Reversals		$0.00
Interest Uncollected on Liquidation		$0.00
Interest Uncollected on Non-Earning Assets		$0.00
Net Unscheduled Interest Distributed		$0.00

OTHER:
Loan Conversion Fees		$0.00
Expense Reimbursements		$0.00
Gain on Liquidations		$0.00
Hazard Insurance Premium Refunds		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$18,297.13

UNSCHEDULED SERVICING FEES:
Unscheduled Service Fee Collections/Reversals		$0.00
Servicing Fees Uncollected on Liquidation		$0.00
Servicing Fees Uncollected/Non-Earning Assets		$0.00
Net Unscheduled Service Fees Distributed		$0.00

MISCELLANEOUS EXPENSES:		$0.00

NET FUNDS DISTRIBUTED:		$223,316.98

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4 WEIGHTED AVERAGE PC RATE: 4.38349%
POOL NUMBER: 2186
ISSUE DATE: 08/29/2003
CERTIFICATE BALANCE AT ISSUE: $55,918,485.87
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	111		$55,918,485.87
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$12,803.49
Unscheduled Principal Collection/Reversals		$162.56
Liquidations-in-full	0	$0.00
Net principal Distributed		$12,966.05	-$12,966.05

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	111		$55,905,519.82

SCHEDULED INTEREST AT MORTGAGE RATE:		$222,904.61

UNSCHEDULED INTEREST AT MORTGAGE RATE:
Unscheduled Interest Collection/Reversals		$0.00
Interest Uncollected on Liquidation		$0.00
Interest Uncollected on Non-Earning Assets		$0.00
Net Unscheduled Interest Distributed		$0.00

OTHER:
Loan Conversion Fees		$0.00
Expense Reimbursements		$0.00
Gain on Liquidations		$0.00
Hazard Insurance Premium Refunds		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$18,639.55

UNSCHEDULED SERVICING FEES:
Unscheduled Service Fee Collections/Reversals		$0.00
Servicing Fees Uncollected on Liquidation		$0.00
Servicing Fees Uncollected/Non-Earning Assets		$0.00
Net Unscheduled Service Fees Distributed		$0.00

MISCELLANEOUS EXPENSES:		$0.00

NET FUNDS DISTRIBUTED:		$217,231.11

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4 WEIGHTED AVERAGE PC RATE: 4.76816%
POOL NUMBER: ALL
ISSUE DATE: 08/29/2003
CERTIFICATE BALANCE AT ISSUE: $914,370,293.51
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	2659		$914,370,293.51
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$183,615.12
Unscheduled Principal Collection/Reversals		$63,788.57
Liquidations-in-full	9	$5,122,525.40
Net principal Distributed		$5,369,929.09	-$5,369,929.09

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	2650		$909,000,364.42

SCHEDULED INTEREST AT MORTGAGE RATE:		$3,938,007.73

UNSCHEDULED INTEREST AT MORTGAGE RATE:
Unscheduled Interest Collection/Reversals		$0.00
Interest Uncollected on Liquidation		$0.00
Interest Uncollected on Non-Earning Assets		$0.00
Net Unscheduled Interest Distributed		$0.00

OTHER:
Loan Conversion Fees		$0.00
Expense Reimbursements		$0.00
Gain on Liquidations		$0.00
Hazard Insurance Premium Refunds		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$304,789.94

UNSCHEDULED SERVICING FEES:
Unscheduled Service Fee Collections/Reversals		$0.00
Servicing Fees Uncollected on Liquidation		$0.00
Servicing Fees Uncollected/Non-Earning Assets		$0.00
Net Unscheduled Service Fees Distributed		$0.00

MISCELLANEOUS EXPENSES:		$0.00

NET FUNDS DISTRIBUTED:		$9,003,146.88

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 09/25/2003

Distribution by Group
Pool ID		Principal		Interest		Total
Group 1(2180,2181,2182,2183,2184,2185,2186)		$5,369,929.09		$3,633,217.79		$9,003,146.88
Pool - 2180		$2,537,095.52		$489,399.30		$3,026,494.82
Pool - 2181		$2,484,712.30		$1,727,474.02		$4,212,186.32
Pool - 2182		$17,575.47		$257,681.65		$275,257.12
Pool - 2183		$301,164.69		$669,750.16		$970,914.85
Pool - 2184		$6,740.66		$71,005.02		$77,745.68
Pool - 2185		$9,674.40		$213,642.58		$223,316.98
Pool - 2186		$12,966.05		$204,265.06		$217,231.11
Aggregate		$5,369,929.09		$3,633,217.79		$9,003,146.88

Number of Loans and Aggregate Principal Balance By Group
Pool ID	Beg Bal	Beg Count	Paid Off / Liq Count	Rem Count	Sched Prin End Bal	Sched Prin	Prin PrePay / Liq	Unsched Prin / Rev	Total Prin
Group 1(2180,2181,2182,2183,2184,2185,2186)	$914,370,293.51	2659	9	2650	$909,000,364.42	$183,615.12	$5,122,525.40	$63,788.57	$5,369,929.09
Pool - 2180	$127,289,895.54	252	4	248	$124,752,800.02	$25,574.53	$2,509,428.02	$2,092.97	$2,537,095.52
Pool - 2181	$427,844,880.53	852	4	848	$425,360,168.23	$77,699.27	$2,352,800.00	$54,213.03	$2,484,712.30
Pool - 2182	$67,014,291.78	334	0	334	$66,996,716.31	$16,513.18	$0.00	$1,062.29	$17,575.47
Pool - 2183	$161,685,471.62	768	1	767	$161,384,306.93	$36,576.81	$260,297.38	$4,290.50	$301,164.69
Pool - 2184	$19,725,894.94	92	0	92	$19,719,154.28	$5,578.74	$0.00	$1,161.92	$6,740.66
Pool - 2185	$54,891,373.23	250	0	250	$54,881,698.83	$8,869.10	$0.00	$805.30	$9,674.40
Pool - 2186	$55,918,485.87	111	0	111	$55,905,519.82	$12,803.49	$0.00	$162.56	$12,966.05
Aggregate	$914,370,293.51	2659	9	2650	$909,000,364.42	$183,615.12	$5,122,525.40	$63,788.57	$5,369,929.09

Delinquency Information by Group
Pool ID	1 Month Count	Sched End Balance	2 Months Count	Sched End Balance	3 Months Count	Sched End Balance	4 Months Count	Sched End Balance
Group 1(2180,2181,2182,2183,2184,2185,2186)	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Pool - 2180	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Pool - 2181	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Pool - 2182	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Pool - 2183	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Pool - 2184	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Pool - 2185	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Pool - 2186	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Aggregate	0	$0.00	0	$0.00	0	$0.00	0	$0.00

Foreclosure and REO Information by Group
Pool ID		Foreclosure Count		Sched End Balance		REO Count		Sched End Balance
Group 1(2180,2181,2182,2183,2184,2185,2186)		0		$0.00		0		$0.00
Pool - 2180		0		$0.00		0		$0.00
Pool - 2181		0		$0.00		0		$0.00
Pool - 2182		0		$0.00		0		$0.00
Pool - 2183		0		$0.00		0		$0.00
Pool - 2184		0		$0.00		0		$0.00
Pool - 2185		0		$0.00		0		$0.00
Pool - 2186		0		$0.00		0		$0.00
Aggregate		0		$0.00		0		$0.00

Aggregate Loss Amounts by Group
Pool ID			Count			Loss Amount
Group 1(2180,2181,2182,2183,2184,2185,2186)			0			$0.00
Aggregate			0			$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 09/25/2003

INSURANCE RESERVES - Group 1(2180,2181,2182,2183,2184,2185,2186)
Insurance Type	Original Balance	Claims In Progress	Claims Paid	Coverage Adjustments	Coverage Remaining
MPI	$0.00	$0.00	$0.00	$0.00	$0.00
Special Hazard	$9,143,702.00	$0.00	$0.00	$0.00	$9,143,702.00
Bankruptcy Bond
Single-Units	$428,906.00	$0.00	$0.00	$0.00	$428,906.00
Multi-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Mortgage Repurchase	$18,287,405.00	$0.00	$0.00	$0.00	$18,287,405.00

INSURANCE RESERVES - Aggregate
Insurance Type	Original Balance	Claims In Progress	Claims Paid	Coverage Adjustments	Coverage Remaining
MPI	$0.00	$0.00	$0.00	$0.00	$0.00
Special Hazard	$9,143,702.00	$0.00	$0.00	$0.00	$9,143,702.00
Bankruptcy Bond
Single-Units	$428,906.00	$0.00	$0.00	$0.00	$428,906.00
Multi-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Mortgage Repurchase	$18,287,405.00	$0.00	$0.00	$0.00	$18,287,405.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 09/25/2003

The Group B Certificates provide, to the limited extent described in the Prospectus Supplement, credit support, as well as special hazard, bankruptcy, and fraud coverage to certain Group I, II, III, IV,V,VI and VII Certificates. The "Prospectus Supplement" is that certain Prospectus Supplement, dated August 27, 2003 to that certain Prospectus Supplement, dated May 20, 2003, to which certain Group I, II, III, IV, V, VI, and VII Certificates were offered. The Special Hazard, Bankruptcy, and Fraud coverage (collectively, "Credit Enhancements") provided by the B certificates provide coverage to the Group I, II, III, IV,V, VI, and VII Loans, subject to the conditions and limitations to payment specified thereunder.



The Class Principal Balances of each Class of the Class M,B1,B2,B3,B4,B5,B6 Certificatesimmediately after the principal and interest distribution on 200309 are as follows:

Class			Class Principal Balance
M			$34,739,022.64
B1			$20,112,060.48
B2			$9,141,963.83
B3			$9,141,763.87
B4			$11,884,413.01
B5			$3,199,657.35
B6			$3,200,050.74
Total			$91,418,931.90
Capitalized items used but not defined herein have the meanings ascribed to them in the Prospectus Supplement.
The amount of the special hazard coverage, bankruptcy coverage, and fraud coverage, as of the above referenced distribution date, is $9,143,702.00, $428,906.00, $18,287,405.00 respectively, and such coverages are referred to in the table above under the column "Insurance Type" as "special hazard," "bankruptcy bond," and "mortgage repurchase," respectively. However, no policy of insurance exists for any such coverage, notwithstanding the reference to "insurance."

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 09/25/2003

Aggregate ARM Information by Group
Pool ID	Netwac	Margin
Group 1(2180,2181,2182,2183,2184,2185,2186)	4.76816%	1.85294%
Pool - 2180	4.61371%	1.85314%
Pool - 2181	4.84514%	1.85131%
Pool - 2182	4.61421%	1.85894%
Pool - 2183	4.97076%	1.85378%
Pool - 2184	4.31950%	1.85362%
Pool - 2185	4.67052%	1.85400%
Pool - 2186	4.38349%	1.85407%
Aggregate	4.76816%	1.85293%

WASHINGTON MUTUAL MORT SEC CORP PASS THR CERT SE 2003-AR4 8-K