WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 10/27/2003

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	Subsequent Recoveries	Total Dist	Ending Class Bal
IA	939336J20	$114,560,800.00	$112,026,361.93	4.6185426074%	4.6185426074%	$431,165.44	$4,155,078.03	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$4,586,243.47	$107,871,283.90
IIA1	939336J38	$29,038,500.00	$28,851,706.68	4.1975481202%	4.1975481202%	$100,922.02	$175,337.17	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$276,259.19	$28,676,369.51
IIA2	939336L27	$356,021,800.00	$353,731,650.96	4.2315481202%	4.2315481202%	$1,247,360.42	$2,149,692.79	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$3,397,053.21	$351,581,958.17
IIIA	939336J53	$60,312,800.00	$60,296,875.86	4.6142000323%	4.6142000323%	$231,851.54	$300,249.13	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$532,100.67	$59,996,626.73
IVA	939336J61	$145,516,900.00	$145,219,393.00	4.9705584822%	4.9705584822%	$601,517.90	$810,649.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,412,166.90	$144,408,744.00
VA	939336J79	$17,753,300.00	$17,747,117.22	4.3195067052%	4.3195067052%	$63,882.33	$183,599.23	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$247,481.56	$17,563,517.99
VIA	939336J87	$49,402,200.00	$49,393,412.52	4.6705163022%	4.6705163022%	$192,243.95	$272,976.96	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$465,220.91	$49,120,435.56
VIIA	939336J95	$50,326,600.00	$50,314,914.31	4.3834844440%	4.3834844440%	$183,795.54	$840,763.71	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,024,559.24	$49,474,150.60
IIX	939336J95	$385,060,300.00	$382,583,357.64	0.6135640374%	0.6135640374%	$195,616.16	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$195,616.16	$380,258,327.68
M	939336K28	$34,746,000.00	$34,739,022.64	4.7675803618%	4.7675803618%	$138,017.57	$7,063.65	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$145,081.22	$34,731,958.99
B1	939336K36	$20,116,100.00	$20,112,060.48	4.7675803618%	4.7675803618%	$79,904.89	$4,089.48	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$83,994.37	$20,107,971.00
B2	939336K44	$9,143,800.00	$9,141,963.83	4.7675803618%	4.7675803618%	$36,320.87	$1,858.88	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$38,179.75	$9,140,104.95
B3	939336K51	$9,143,600.00	$9,141,763.87	4.7675803618%	4.7675803618%	$36,320.08	$1,858.84	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$38,178.92	$9,139,905.03
B4	939336K77	$11,886,800.00	$11,884,413.01	4.7675803618%	4.7675803618%	$47,216.58	$2,416.51	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$49,633.09	$11,881,996.50
B5	939336K85	$3,200,300.00	$3,199,657.35	4.7675803618%	4.7675803618%	$12,712.19	$650.60	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$13,362.79	$3,199,006.75
B6	939336K93	$3,200,693.47	$3,200,050.74	4.7675803618%	4.7675803618%	$12,713.75	$650.68	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$13,364.43	$3,199,400.06
R	939336K69	$100.00	$0.00	0.0000000000%	0.0000000000%	$0.45	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.45	$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	$0.00
Total		$914,370,293.47	$909,000,364.40			$3,611,561.66	$8,906,934.67	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$12,518,496.33	$900,093,429.73

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 10/27/2003

Class	Orig Face	Beg Bal	Prin Loss	Prin Reimbursed	Subsequent Recoveries	Deferred Interest	Total Prin	End Cert Pct	End Cert Bal
IA	$114,560,800.00	$112,026,361.93	$0.00	$0.00	$0.00	$0.00	$4,155,078.03	0.9416072854	$107,871,283.90
IIA1	$29,038,500.00	$28,851,706.68	$0.00	$0.00	$0.00	$0.00	$175,337.17	0.9875292977	$28,676,369.51
IIA2	$356,021,800.00	$353,731,650.96	$0.00	$0.00	$0.00	$0.00	$2,149,692.79	0.9875292978	$351,581,958.17
IIIA	$60,312,800.00	$60,296,875.86	$0.00	$0.00	$0.00	$0.00	$300,249.13	0.9947577750	$59,996,626.73
IVA	$145,516,900.00	$145,219,393.00	$0.00	$0.00	$0.00	$0.00	$810,649.00	0.9923846921	$144,408,744.00
VA	$17,753,300.00	$17,747,117.22	$0.00	$0.00	$0.00	$0.00	$183,599.23	0.9893100432	$17,563,517.99
VIA	$49,402,200.00	$49,393,412.52	$0.00	$0.00	$0.00	$0.00	$272,976.96	0.9942965204	$49,120,435.56
VIIA	$50,326,600.00	$50,314,914.31	$0.00	$0.00	$0.00	$0.00	$840,763.71	0.9830616533	$49,474,150.60
IIX	$385,060,300.00	$382,583,357.64	$0.00	$0.00	$0.00	$0.00	$0.00	0.9875292978	$380,258,327.68
M	$34,746,000.00	$34,739,022.64	$0.00	$0.00	$0.00	$0.00	$7,063.65	0.9995958956	$34,731,958.99
B1	$20,116,100.00	$20,112,060.48	$0.00	$0.00	$0.00	$0.00	$4,089.48	0.9995958958	$20,107,971.00
B2	$9,143,800.00	$9,141,963.83	$0.00	$0.00	$0.00	$0.00	$1,858.88	0.9995958956	$9,140,104.95
B3	$9,143,600.00	$9,141,763.87	$0.00	$0.00	$0.00	$0.00	$1,858.84	0.9995958955	$9,139,905.03
B4	$11,886,800.00	$11,884,413.01	$0.00	$0.00	$0.00	$0.00	$2,416.51	0.9995958963	$11,881,996.50
B5	$3,200,300.00	$3,199,657.35	$0.00	$0.00	$0.00	$0.00	$650.60	0.9995958973	$3,199,006.75
B6	$3,200,693.47	$3,200,050.74	$0.00	$0.00	$0.00	$0.00	$650.68	0.9995958969	$3,199,400.06
R	$100.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
R_SYN	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
Total	$914,370,293.47	$909,000,364.40	$0.00	$0.00	$0.00	$0.00	$8,906,934.67	0.9843861247	$900,093,429.73

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 10/27/2003
PER $1000 DENOMINATION
Class	Orig Face	Beg Bal	Prin Loss	Prin Reimbursed	Subsequent Recoveries	Deferred Interest	Total Prin	End Cert Pct	End Cert Bal
IA	$114,560,800.00	977.87691715	0.00000000	0.00000000	0.00000000	0.00000000	36.26963176	0.9416072854	941.60728539
IIA1	$29,038,500.00	993.56739088	0.00000000	0.00000000	0.00000000	0.00000000	6.03809322	0.9875292977	987.52929766
IIA2	$356,021,800.00	993.56739099	0.00000000	0.00000000	0.00000000	0.00000000	6.03809314	0.9875292978	987.52929784
IIIA	$60,312,800.00	999.73597412	0.00000000	0.00000000	0.00000000	0.00000000	4.97819916	0.9947577750	994.75777497
IVA	$145,516,900.00	997.95551582	0.00000000	0.00000000	0.00000000	0.00000000	5.57082373	0.9923846921	992.38469209
VA	$17,753,300.00	999.65173911	0.00000000	0.00000000	0.00000000	0.00000000	10.34169591	0.9893100432	989.31004320
VIA	$49,402,200.00	999.82212371	0.00000000	0.00000000	0.00000000	0.00000000	5.52560331	0.9942965204	994.29652040
VIIA	$50,326,600.00	999.76780291	0.00000000	0.00000000	0.00000000	0.00000000	16.70614963	0.9830616533	983.06165328
IIX	$385,060,300.00	993.56739098	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.9875292978	987.52929783
M	$34,746,000.00	999.79918955	0.00000000	0.00000000	0.00000000	0.00000000	0.20329390	0.9995958956	999.59589564
B1	$20,116,100.00	999.79918970	0.00000000	0.00000000	0.00000000	0.00000000	0.20329388	0.9995958958	999.59589582
B2	$9,143,800.00	999.79918961	0.00000000	0.00000000	0.00000000	0.00000000	0.20329404	0.9995958956	999.59589558
B3	$9,143,600.00	999.79918960	0.00000000	0.00000000	0.00000000	0.00000000	0.20329411	0.9995958955	999.59589549
B4	$11,886,800.00	999.79918986	0.00000000	0.00000000	0.00000000	0.00000000	0.20329357	0.9995958963	999.59589629
B5	$3,200,300.00	999.79919070	0.00000000	0.00000000	0.00000000	0.00000000	0.20329344	0.9995958973	999.59589726
B6	$3,200,693.47	999.79919039	0.00000000	0.00000000	0.00000000	0.00000000	0.20329344	0.9995958969	999.59589695
R	$100.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
R_SYN	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 10/27/2003

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	4.6185426074%	4.6185426074%	$112,026,361.93	$431,165.44	$0.00	$0.00	$0.00	$431,165.44
IIA1	$29,038,500.00	4.1975481202%	4.1975481202%	$28,851,706.68	$100,922.02	$0.00	$0.00	$0.00	$100,922.02
IIA2	$356,021,800.00	4.2315481202%	4.2315481202%	$353,731,650.96	$1,247,360.42	$0.00	$0.00	$0.00	$1,247,360.42
IIIA	$60,312,800.00	4.6142000323%	4.6142000323%	$60,296,875.86	$231,851.54	$0.00	$0.00	$0.00	$231,851.54
IVA	$145,516,900.00	4.9705584822%	4.9705584822%	$145,219,393.00	$601,517.90	$0.00	$0.00	$0.00	$601,517.90
VA	$17,753,300.00	4.3195067052%	4.3195067052%	$17,747,117.22	$63,882.33	$0.00	$0.00	$0.00	$63,882.33
VIA	$49,402,200.00	4.6705163022%	4.6705163022%	$49,393,412.52	$192,243.95	$0.00	$0.00	$0.00	$192,243.95
VIIA	$50,326,600.00	4.3834844440%	4.3834844440%	$50,314,914.31	$183,795.54	$0.00	$0.00	$0.00	$183,795.54
IIX	$385,060,300.00	0.6135640374%	0.6135640374%	$382,583,357.64	$195,616.16	$0.00	$0.00	$0.00	$195,616.16
M	$34,746,000.00	4.7675803618%	4.7675803618%	$34,739,022.64	$138,017.57	$0.00	$0.00	$0.00	$138,017.57
B1	$20,116,100.00	4.7675803618%	4.7675803618%	$20,112,060.48	$79,904.89	$0.00	$0.00	$0.00	$79,904.89
B2	$9,143,800.00	4.7675803618%	4.7675803618%	$9,141,963.83	$36,320.87	$0.00	$0.00	$0.00	$36,320.87
B3	$9,143,600.00	4.7675803618%	4.7675803618%	$9,141,763.87	$36,320.08	$0.00	$0.00	$0.00	$36,320.08
B4	$11,886,800.00	4.7675803618%	4.7675803618%	$11,884,413.01	$47,216.58	$0.00	$0.00	$0.00	$47,216.58
B5	$3,200,300.00	4.7675803618%	4.7675803618%	$3,199,657.35	$12,712.19	$0.00	$0.00	$0.00	$12,712.19
B6	$3,200,693.47	4.7675803618%	4.7675803618%	$3,200,050.74	$12,713.75	$0.00	$0.00	$0.00	$12,713.75
R	$100.00	0.0000000000%	0.0000000000%	$0.00	$0.45	$0.00	$0.00	$0.00	$0.45
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			$909,000,364.40	$3,611,561.66	$0.00	$0.00	$0.00	$3,611,561.66

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 10/27/2003
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	4.6185426074%	4.6185426074%	977.87691715	3.76363852	0.00000000	0.00000000	0.00000000	3.76363852
IIA1	$29,038,500.00	4.1975481202%	4.1975481202%	993.56739088	3.47545569	0.00000000	0.00000000	0.00000000	3.47545569
IIA2	$356,021,800.00	4.2315481202%	4.2315481202%	993.56739099	3.50360686	0.00000000	0.00000000	0.00000000	3.50360686
IIIA	$60,312,800.00	4.6142000323%	4.6142000323%	999.73597412	3.84415149	0.00000000	0.00000000	0.00000000	3.84415149
IVA	$145,516,900.00	4.9705584822%	4.9705584822%	997.95551582	4.13366351	0.00000000	0.00000000	0.00000000	4.13366351
VA	$17,753,300.00	4.3195067052%	4.3195067052%	999.65173911	3.59833552	0.00000000	0.00000000	0.00000000	3.59833552
VIA	$49,402,200.00	4.6705163022%	4.6705163022%	999.82212371	3.89140463	0.00000000	0.00000000	0.00000000	3.89140463
VIIA	$50,326,600.00	4.3834844440%	4.3834844440%	999.76780291	3.65205557	0.00000000	0.00000000	0.00000000	3.65205557
IIX	$385,060,300.00	0.6135640374%	0.6135640374%	993.56739098	0.50801436	0.00000000	0.00000000	0.00000000	0.50801436
M	$34,746,000.00	4.7675803618%	4.7675803618%	999.79918955	3.97218586	0.00000000	0.00000000	0.00000000	3.97218586
B1	$20,116,100.00	4.7675803618%	4.7675803618%	999.79918970	3.97218596	0.00000000	0.00000000	0.00000000	3.97218596
B2	$9,143,800.00	4.7675803618%	4.7675803618%	999.79918961	3.97218552	0.00000000	0.00000000	0.00000000	3.97218552
B3	$9,143,600.00	4.7675803618%	4.7675803618%	999.79918960	3.97218601	0.00000000	0.00000000	0.00000000	3.97218601
B4	$11,886,800.00	4.7675803618%	4.7675803618%	999.79918986	3.97218595	0.00000000	0.00000000	0.00000000	3.97218595
B5	$3,200,300.00	4.7675803618%	4.7675803618%	999.79919070	3.97218698	0.00000000	0.00000000	0.00000000	3.97218698
B6	$3,200,693.47	4.7675803618%	4.7675803618%	999.79919039	3.97218607	0.00000000	0.00000000	0.00000000	3.97218607
R	$100.00	0.0000000000%	0.0000000000%	0.00000000	4.50000000	0.00000000	0.00000000	0.00000000	4.50000000
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
10/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4
WEIGHTED AVERAGE PC RATE: 4.76774%
WEIGHTED AVERAGE MATURITY: 200.89876
WEIGHTED AVERAGE LOAN AGE: 3.57683
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:	2650		$909,000,364.42
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$184,860.25
Unscheduled Principal Collection/Reversals		$644,950.88
Liquidations-in-full	20	$8,077,123.54
Subsequent Recoveries		$0.00
Net principal Distributed		$8,906,934.67	-$8,906,934.67

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	2630		$900,093,429.75

SCHEDULED INTEREST AT MORTGAGE RATE:		$3,914,561.87

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
Recoveries Carried Forward		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$303,000.21

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:		$12,518,496.33

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4
WEIGHTED AVERAGE PC RATE: 4.61854%
WEIGHTED AVERAGE MATURITY: 206.30116
WEIGHTED AVERAGE LOAN AGE: 3.62736
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:	248		$124,752,800.02
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$25,963.05
Unscheduled Principal Collection/Reversals		$26,122.54
Liquidations-in-full	8	$4,105,641.02
Subsequent Recoveries		$0.00
Net principal Distributed		$4,157,726.61	-$4,157,726.61

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	240		$120,595,073.41

SCHEDULED INTEREST AT MORTGAGE RATE:		$521,731.10

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
Recoveries Carried Forward		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$41,584.28

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:		$4,637,873.43

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4
WEIGHTED AVERAGE PC RATE: 4.84255%
WEIGHTED AVERAGE MATURITY: 192.74488
WEIGHTED AVERAGE LOAN AGE: 3.50907
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:	848		$425,360,168.23
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$78,041.69
Unscheduled Principal Collection/Reversals		$296,234.50
Liquidations-in-full	3	$1,958,602.12
Subsequent Recoveries		$0.00
Net principal Distributed		$2,332,878.31	-$2,332,878.31

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	845		$423,027,289.92

SCHEDULED INTEREST AT MORTGAGE RATE:		$1,858,309.42

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
Recoveries Carried Forward		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$141,786.70

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:		$4,049,401.03

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4
WEIGHTED AVERAGE PC RATE: 4.61420%
WEIGHTED AVERAGE MATURITY: 221.78457
WEIGHTED AVERAGE LOAN AGE: 3.89448
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		$66,996,716.31
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$16,586.44
Unscheduled Principal Collection/Reversals		$13,357.08
Liquidations-in-full	2	$271,964.30
Subsequent Recoveries		$0.00
Net principal Distributed		$301,907.82	-$301,907.82

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	332		$66,694,808.49

SCHEDULED INTEREST AT MORTGAGE RATE:		$279,945.84

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
Recoveries Carried Forward		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$22,332.15

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:		$559,521.51

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4
WEIGHTED AVERAGE PC RATE: 4.97056%
WEIGHTED AVERAGE MATURITY: 208.25094
WEIGHTED AVERAGE LOAN AGE: 3.89968
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:	767		$161,384,306.93
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$36,891.57
Unscheduled Principal Collection/Reversals		$2,055.02
Liquidations-in-full	4	$775,397.62
Subsequent Recoveries		$0.00
Net principal Distributed		$814,344.21	-$814,344.21

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	763		$160,569,962.72

SCHEDULED INTEREST AT MORTGAGE RATE:		$722,270.05

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
Recoveries Carried Forward		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$53,794.90

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:		$1,482,819.36

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4
WEIGHTED AVERAGE PC RATE: 4.31951%
WEIGHTED AVERAGE MATURITY: 231.21527
WEIGHTED AVERAGE LOAN AGE: 3.02110
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		$19,719,154.28
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$5,603.52
Unscheduled Principal Collection/Reversals		$2,056.10
Liquidations-in-full	1	$176,500.00
Subsequent Recoveries		$0.00
Net principal Distributed		$184,159.62	-$184,159.62

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	91		$19,534,994.66

SCHEDULED INTEREST AT MORTGAGE RATE:		$77,553.93

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
Recoveries Carried Forward		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$6,573.04

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:		$255,140.51

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4
WEIGHTED AVERAGE PC RATE: 4.67052%
WEIGHTED AVERAGE MATURITY: 205.20367
WEIGHTED AVERAGE LOAN AGE: 3.06995
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		$54,881,698.83
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$8,906.68
Unscheduled Principal Collection/Reversals		$8,960.97
Liquidations-in-full	1	$256,000.00
Subsequent Recoveries		$0.00
Net principal Distributed		$273,867.65	-$273,867.65

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	249		$54,607,831.18

SCHEDULED INTEREST AT MORTGAGE RATE:		$231,898.83

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
Recoveries Carried Forward		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$18,293.91

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:		$487,472.57

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4
WEIGHTED AVERAGE PC RATE: 4.38348%
WEIGHTED AVERAGE MATURITY: 189.94750
WEIGHTED AVERAGE LOAN AGE: 3.36041
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		$55,905,519.82
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$12,867.30
Unscheduled Principal Collection/Reversals		$296,164.67
Liquidations-in-full	1	$533,018.48
Subsequent Recoveries		$0.00
Net principal Distributed		$842,050.45	-$842,050.45

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	110		$55,063,469.37

SCHEDULED INTEREST AT MORTGAGE RATE:		$222,852.70

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
Recoveries Carried Forward		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$18,635.23

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:		$1,046,267.92

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
SERIES: WAMMS 03AR4
WEIGHTED AVERAGE PC RATE: 4.76774%
WEIGHTED AVERAGE MATURITY: 200.89876
WEIGHTED AVERAGE LOAN AGE: 3.57683
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:	2650		$909,000,364.42
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$184,860.25
Unscheduled Principal Collection/Reversals		$644,950.88
Liquidations-in-full	20	$8,077,123.54
Subsequent Recoveries		$0.00
Net principal Distributed		$8,906,934.67	-$8,906,934.67

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	2630		$900,093,429.75

SCHEDULED INTEREST AT MORTGAGE RATE:		$3,914,561.87

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
Recoveries Carried Forward		$0.00
Net Other Distributions		$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
10/2003 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$303,000.21

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:		$12,518,496.33

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03AR4
Distribution Date: 10/27/2003

Distribution by Group
Pool ID		Principal		Interest		Total
Group 1(2180,2181,2182,2183,2184,2185,2186)		$8,906,934.67		$3,611,561.66		$12,518,496.33
Pool - 2180		$4,157,726.61		$480,146.82		$4,637,873.43
Pool - 2181		$2,332,878.31		$1,716,522.72		$4,049,401.03
Pool - 2182		$301,907.82		$257,613.69		$559,521.51
Pool - 2183		$814,344.21		$668,475.15		$1,482,819.36
Pool - 2184		$184,159.62		$70,980.89		$255,140.51
Pool - 2185		$273,867.65		$213,604.92		$487,472.57
Pool - 2186		$842,050.45		$204,217.47		$1,046,267.92
Aggregate		$8,906,934.67		$3,611,561.66		$12,518,496.33

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)	$909,000,364.42	2650	20	2630	$900,093,429.75	$184,860.25	$8,077,123.54	$644,950.88	$8,906,934.67
Pool - 2180	$124,752,800.02	248	8	240	$120,595,073.41	$25,963.05	$4,105,641.02	$26,122.54	$4,157,726.61
Pool - 2181	$425,360,168.23	848	3	845	$423,027,289.92	$78,041.69	$1,958,602.12	$296,234.50	$2,332,878.31
Pool - 2182	$66,996,716.31	334	2	332	$66,694,808.49	$16,586.44	$271,964.30	$13,357.08	$301,907.82
Pool - 2183	$161,384,306.93	767	4	763	$160,569,962.72	$36,891.57	$775,397.62	$2,055.02	$814,344.21
Pool - 2184	$19,719,154.28	92	1	91	$19,534,994.66	$5,603.52	$176,500.00	$2,056.10	$184,159.62
Pool - 2185	$54,881,698.83	250	1	249	$54,607,831.18	$8,906.68	$256,000.00	$8,960.97	$273,867.65
Pool - 2186	$55,905,519.82	111	1	110	$55,063,469.37	$12,867.30	$533,018.48	$296,164.67	$842,050.45
Aggregate	$909,000,364.42	2650	20	2630	$900,093,429.75	$184,860.25	$8,077,123.54	$644,950.88	$8,906,934.67

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)	60	$21,331,022.25	0	$0.00	0	$0.00	0	$0.00
Pool - 2180	6	$4,196,541.67	0	$0.00	0	$0.00	0	$0.00
Pool - 2181	14	$7,300,831.41	0	$0.00	0	$0.00	0	$0.00
Pool - 2182	7	$1,724,275.59	0	$0.00	0	$0.00	0	$0.00
Pool - 2183	20	$3,804,614.46	0	$0.00	0	$0.00	0	$0.00
Pool - 2184	2	$243,509.76	0	$0.00	0	$0.00	0	$0.00
Pool - 2185	5	$1,051,000.00	0	$0.00	0	$0.00	0	$0.00
Pool - 2186	6	$3,010,249.36	0	$0.00	0	$0.00	0	$0.00
Aggregate	60	$21,331,022.25	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: 10/27/2003

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: 10/27/2003

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 200310 are as follows:

Class			Class Principal Balance
M			$34,731,958.99
B1			$20,107,971.00
B2			$9,140,104.95
B3			$9,139,905.03
B4			$11,881,996.50
B5			$3,199,006.75
B6			$3,199,400.06
Total			$91,400,343.28
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: 10/27/2003

Aggregate ARM Information by Group
Pool ID	Netwac	Margin
Group 1(2180,2181,2182,2183,2184,2185,2186)	4.76774%	1.85297%
Pool - 2180	4.61854%	1.85325%
Pool - 2181	4.84255%	1.85131%
Pool - 2182	4.61420%	1.85897%
Pool - 2183	4.97056%	1.85379%
Pool - 2184	4.31951%	1.85365%
Pool - 2185	4.67052%	1.85402%
Pool - 2186	4.38348%	1.85413%
Aggregate	4.76774%	1.85294%

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