WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03MS4
Distribution Date: 09/27/2004

Class	Cusip	Orig Prin Bal	Begin Prin Bal	Int Rate Accrued	Int Rate Paid	Int Dist	Prin Dist	Int Shortfall	PPIS	Uncomp Int Shortfall	Prin Loss	Deferred Interest	Int Reimbursed	Unsched Int	Prin Reimbursed	Subsequent Recoveries	Total Dist	Ending Class Bal
IA1	939336XW8	$215,141,235.00	$58,896,791.69	2.1250000000%	2.1250000000%	$104,296.40	$1,474,853.44	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,579,149.85	$57,421,938.25
IA2	939336XX6	$117,349,765.00	$32,125,522.87	11.6875038750%	11.6875038750%	$312,889.31	$804,465.52	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,117,354.83	$31,321,057.35
IIA1	939336XY4	$67,648,000.00	$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	$0.00	$0.00
IIA2	939336XZ1	$22,549,333.00	$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	$0.00	$0.00
IIA3	939336YA5	$136,786,429.00	$67,122,327.20	5.0000000000%	5.0000000000%	$279,676.36	$1,604,582.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,884,258.36	$65,517,745.20
IIA4	939336YB3	$54,714,571.00	$26,848,930.58	2.0750000000%	2.0750000000%	$46,426.28	$641,832.79	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$688,259.07	$26,207,097.79
IIA5	939336YC1	$54,714,571.00	$26,848,930.58	6.4250000000%	6.4250000000%	$143,753.65	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$143,753.65	$26,207,097.79
IIA6	939336YD9	$12,368,932.00	$12,368,932.00	6.0000000000%	6.0000000000%	$61,844.66	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$61,844.66	$12,368,932.00
IIA7	939336YE7	$99,116,054.00	$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	$0.00	$0.00
IIA8	939336YF4	$24,779,014.00	$0.01	17.6200000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.01
IIA9	939336YG2	$54,750,000.00	$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	$0.00	$0.00
IIA10	939336YH0	$2,281,250.00	$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	$0.00	$0.00
IIIA1	939336YJ6	$59,614,000.00	$33,758,141.42	4.7500000000%	4.7500000000%	$133,625.98	$413,992.27	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$547,618.24	$33,344,149.15
IIIA2	939336YK3	$8,129,181.00	$4,603,382.92	5.5000000000%	5.5000000000%	$21,098.84	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$21,098.84	$4,546,929.43
IIIA3	939336YL1	$3,198,000.00	$3,472,369.19	5.5000000000%	5.5000000000%	$15,915.03	($15,915.03)	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$3,488,284.22
IIX	939336YM9	$14,924,708.00	$2,539,761.95	6.0000000000%	6.0000000000%	$12,698.81	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$12,698.81	$2,448,626.15
IIIX	939336YN7	$1,392,783.00	$788,258.40	5.5000000000%	5.5000000000%	$3,612.85	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$3,612.85	$774,584.79
IP	939336YP2	$4,774,932.00	$2,413,113.83	0.0000000000%	0.0000000000%	$0.00	$20,895.79	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$20,895.79	$2,392,218.04
AP	939336YQ0	$3,195,695.58	$1,225,073.61	0.0000000000%	0.0000000000%	$0.00	$8,805.98	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$8,805.98	$1,216,267.63
CB1	939336YR8	$8,278,000.00	$7,925,132.14	5.7703413037%	5.7703413037%	$38,108.93	$19,150.91	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$57,259.84	$7,905,981.23
CB2	939336YS6	$4,357,000.00	$4,171,273.32	5.7703413037%	5.7703413037%	$20,058.06	$10,079.79	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$30,137.85	$4,161,193.53
CB3	939336YT4	$2,178,000.00	$2,085,157.97	5.7703413037%	5.7703413037%	$10,026.73	$5,038.74	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$15,065.47	$2,080,119.23
CB4	939336UB7	$871,000.00	$833,871.71	5.7703413037%	5.7703413037%	$4,009.77	$2,015.03	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$6,024.80	$831,856.68
CB5	939336UC5	$871,000.00	$833,871.71	5.7703413037%	5.7703413037%	$4,009.77	$2,015.03	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$6,024.80	$831,856.68
CB6	939336UD3	$1,308,002.51	$1,252,246.06	5.7703413037%	5.7703413037%	$6,021.57	$3,025.86	$0.00	$0.00	$0.00	$0.15	$0.00	$0.00	$0.00	$0.00	$0.00	$9,047.44	$1,249,220.04
R	939336YU1	$100.00	$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	$0.00	$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	$0.00	$0.00
Total		$871,299,730.09	$255,332,755.31			$1,218,072.99	$4,994,838.14	$0.00	$0.00	$0.00	$0.15	$0.00	$0.00	$0.00	$0.00	$0.00	$6,212,911.13	$250,337,917.02

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03MS4
Distribution Date: 09/27/2004

Class	Orig Face	Beg Bal	Prin Loss	Prin Reimbursed	Subsequent Recoveries	Deferred Interest	Total Prin	End Cert Pct	End Cert Bal
IA1	$215,141,235.00	$58,896,791.69	$0.00	$0.00	$0.00	$0.00	$1,474,853.44	0.2669034518	$57,421,938.25
IA2	$117,349,765.00	$32,125,522.87	$0.00	$0.00	$0.00	$0.00	$804,465.52	0.2669034518	$31,321,057.35
IIA1	$67,648,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
IIA2	$22,549,333.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
IIA3	$136,786,429.00	$67,122,327.20	$0.00	$0.00	$0.00	$0.00	$1,604,582.00	0.4789784022	$65,517,745.20
IIA4	$54,714,571.00	$26,848,930.58	$0.00	$0.00	$0.00	$0.00	$641,832.79	0.4789784021	$26,207,097.79
IIA5	$54,714,571.00	$26,848,930.58	$0.00	$0.00	$0.00	$0.00	$0.00	0.4789784021	$26,207,097.79
IIA6	$12,368,932.00	$12,368,932.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$12,368,932.00
IIA7	$99,116,054.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
IIA8	$24,779,014.00	$0.01	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000004	$0.01
IIA9	$54,750,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
IIA10	$2,281,250.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
IIIA1	$59,614,000.00	$33,758,141.42	$0.00	$0.00	$0.00	$0.00	$413,992.27	0.5593342025	$33,344,149.15
IIIA2	$8,129,181.00	$4,603,382.92	$0.00	$0.00	$0.00	$0.00	$0.00	0.5593342589	$4,546,929.43
IIIA3	$3,198,000.00	$3,472,369.19	$0.00	$0.00	$0.00	$0.00	($15,915.03)	1.0907705503	$3,488,284.22
IIX	$14,924,708.00	$2,539,761.95	$0.00	$0.00	$0.00	$0.00	$0.00	0.1640652635	$2,448,626.15
IIIX	$1,392,783.00	$788,258.40	$0.00	$0.00	$0.00	$0.00	$0.00	0.5561417608	$774,584.79
IP	$4,774,932.00	$2,413,113.83	$0.00	$0.00	$0.00	$0.00	$20,895.79	0.5009952058	$2,392,218.04
AP	$3,195,695.58	$1,225,073.61	$0.00	$0.00	$0.00	$0.00	$8,805.98	0.3805955854	$1,216,267.63
CB1	$8,278,000.00	$7,925,132.14	$0.00	$0.00	$0.00	$0.00	$19,150.91	0.9550593416	$7,905,981.23
CB2	$4,357,000.00	$4,171,273.32	$0.00	$0.00	$0.00	$0.00	$10,079.79	0.9550593367	$4,161,193.53
CB3	$2,178,000.00	$2,085,157.97	$0.00	$0.00	$0.00	$0.00	$5,038.74	0.9550593343	$2,080,119.23
CB4	$871,000.00	$833,871.71	$0.00	$0.00	$0.00	$0.00	$2,015.03	0.9550593341	$831,856.68
CB5	$871,000.00	$833,871.71	$0.00	$0.00	$0.00	$0.00	$2,015.03	0.9550593341	$831,856.68
CB6	$1,308,002.51	$1,252,246.06	$0.15	$0.00	$0.00	$0.00	$3,025.86	0.9550593599	$1,249,220.04
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	$871,299,730.09	$255,332,755.31	$0.15	$0.00	$0.00	$0.00	$4,994,838.14	0.2873154993	$250,337,917.02

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03MS4
Distribution Date: 09/27/2004
PER $1000 DENOMINATION
Class	Orig Face	Beg Bal	Prin Loss	Prin Reimbursed	Subsequent Recoveries	Deferred Interest	Total Prin	End Cert Pct	End Cert Bal
IA1	$215,141,235.00	273.75873198	0.00000000	0.00000000	0.00000000	0.00000000	6.85528016	0.2669034518	266.90345182
IA2	$117,349,765.00	273.75873203	0.00000000	0.00000000	0.00000000	0.00000000	6.85528020	0.2669034518	266.90345183
IIA1	$67,648,000.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
IIA2	$22,549,333.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
IIA3	$136,786,429.00	490.70896646	0.00000000	0.00000000	0.00000000	0.00000000	11.73056429	0.4789784022	478.97840216
IIA4	$54,714,571.00	490.70896636	0.00000000	0.00000000	0.00000000	0.00000000	11.73056424	0.4789784021	478.97840212
IIA5	$54,714,571.00	490.70896636	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.4789784021	478.97840212
IIA6	$12,368,932.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
IIA7	$99,116,054.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
IIA8	$24,779,014.00	0.00000040	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000004	0.00000040
IIA9	$54,750,000.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
IIA10	$2,281,250.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
IIIA1	$59,614,000.00	566.27875029	0.00000000	0.00000000	0.00000000	0.00000000	6.94454776	0.5593342025	559.33420254
IIIA2	$8,129,181.00	566.27880718	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.5593342589	559.33425889
IIIA3	$3,198,000.00	1,085.79399312	0.00000000	0.00000000	0.00000000	0.00000000	-4.97655722	1.0907705503	1,090.77055034
IIX	$14,924,708.00	170.17163418	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.1640652635	164.06526345
IIIX	$1,392,783.00	565.95923414	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.5561417608	556.14176078
IP	$4,774,932.00	505.37134979	0.00000000	0.00000000	0.00000000	0.00000000	4.37614400	0.5009952058	500.99520580
AP	$3,195,695.58	383.35116075	0.00000000	0.00000000	0.00000000	0.00000000	2.75557536	0.3805955854	380.59558539
CB1	$8,278,000.00	957.37281227	0.00000000	0.00000000	0.00000000	0.00000000	2.31347065	0.9550593416	955.05934163
CB2	$4,357,000.00	957.37280698	0.00000000	0.00000000	0.00000000	0.00000000	2.31347028	0.9550593367	955.05933670
CB3	$2,178,000.00	957.37280533	0.00000000	0.00000000	0.00000000	0.00000000	2.31347107	0.9550593343	955.05933425
CB4	$871,000.00	957.37280138	0.00000000	0.00000000	0.00000000	0.00000000	2.31346728	0.9550593341	955.05933410
CB5	$871,000.00	957.37280138	0.00000000	0.00000000	0.00000000	0.00000000	2.31346728	0.9550593341	955.05933410
CB6	$1,308,002.51	957.37282645	0.00011468	0.00000000	0.00000000	0.00000000	2.31334418	0.9550593599	955.05935994
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.03MS4
Distribution Date: 09/27/2004

Class	Orig Face	Int Rate Accrued	Int Rate Paid	Beg Cert Prin/Not Bal	Current Int Accrued	Int Shortfall	PPIS	Uncompensated Int Shortfall	Unscheduled Int	Int Reimbursed	Total Int Dist
IA1	$215,141,235.00	2.1250000000%	2.1250000000%	$58,896,791.69	$104,296.40	$0.00	$0.00	$0.00	$0.00	$0.00	$104,296.40
IA2	$117,349,765.00	11.6875038750%	11.6875038750%	$32,125,522.87	$312,889.31	$0.00	$0.00	$0.00	$0.00	$0.00	$312,889.31
IIA1	$67,648,000.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
IIA2	$22,549,333.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
IIA3	$136,786,429.00	5.0000000000%	5.0000000000%	$67,122,327.20	$279,676.36	$0.00	$0.00	$0.00	$0.00	$0.00	$279,676.36
IIA4	$54,714,571.00	2.0750000000%	2.0750000000%	$26,848,930.58	$46,426.28	$0.00	$0.00	$0.00	$0.00	$0.00	$46,426.28
IIA5	$54,714,571.00	6.4250000000%	6.4250000000%	$26,848,930.58	$143,753.65	$0.00	$0.00	$0.00	$0.00	$0.00	$143,753.65
IIA6	$12,368,932.00	6.0000000000%	6.0000000000%	$12,368,932.00	$61,844.66	$0.00	$0.00	$0.00	$0.00	$0.00	$61,844.66
IIA7	$99,116,054.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
IIA8	$24,779,014.00	17.6200000000%	0.0000000000%	$0.01	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
IIA9	$54,750,000.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
IIA10	$2,281,250.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
IIIA1	$59,614,000.00	4.7500000000%	4.7500000000%	$33,758,141.42	$133,625.98	$0.00	$0.00	$0.00	$0.00	$0.00	$133,625.98
IIIA2	$8,129,181.00	5.5000000000%	5.5000000000%	$4,603,382.92	$21,098.84	$0.00	$0.00	$0.00	$0.00	$0.00	$21,098.84
IIIA3	$3,198,000.00	5.5000000000%	5.5000000000%	$3,472,369.19	$15,915.03	$0.00	$0.00	$0.00	$0.00	$0.00	$15,915.03
IIX	$14,924,708.00	6.0000000000%	6.0000000000%	$2,539,761.95	$12,698.81	$0.00	$0.00	$0.00	$0.00	$0.00	$12,698.81
IIIX	$1,392,783.00	5.5000000000%	5.5000000000%	$788,258.40	$3,612.85	$0.00	$0.00	$0.00	$0.00	$0.00	$3,612.85
IP	$4,774,932.00	0.0000000000%	0.0000000000%	$2,413,113.83	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
AP	$3,195,695.58	0.0000000000%	0.0000000000%	$1,225,073.61	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
CB1	$8,278,000.00	5.7703413037%	5.7703413037%	$7,925,132.14	$38,108.93	$0.00	$0.00	$0.00	$0.00	$0.00	$38,108.93
CB2	$4,357,000.00	5.7703413037%	5.7703413037%	$4,171,273.32	$20,058.06	$0.00	$0.00	$0.00	$0.00	$0.00	$20,058.06
CB3	$2,178,000.00	5.7703413037%	5.7703413037%	$2,085,157.97	$10,026.73	$0.00	$0.00	$0.00	$0.00	$0.00	$10,026.73
CB4	$871,000.00	5.7703413037%	5.7703413037%	$833,871.71	$4,009.77	$0.00	$0.00	$0.00	$0.00	$0.00	$4,009.77
CB5	$871,000.00	5.7703413037%	5.7703413037%	$833,871.71	$4,009.77	$0.00	$0.00	$0.00	$0.00	$0.00	$4,009.77
CB6	$1,308,002.51	5.7703413037%	5.7703413037%	$1,252,246.06	$6,021.57	$0.00	$0.00	$0.00	$0.00	$0.00	$6,021.57
R	$100.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
R_SYN	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
Total	$871,299,730.09			$255,332,755.31	$1,218,072.99	$0.00	$0.00	$0.00	$0.00	$0.00	$1,218,072.99

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03MS4
Distribution Date: 09/27/2004
PER $1000 DENOMINATION
Class	Orig Face	Int Rate Accrued	Int Rate Paid	Beg Cert Prin/Not Bal	Curent Int Accrued	Int Shortfall	PPIS	Uncompensated Int Shortfall	Unscheduled Int	Int Reimbursed	Total Int Dist
IA1	$215,141,235.00	2.1250000000%	2.1250000000%	273.75873198	0.48478108	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.48478108
IA2	$117,349,765.00	11.6875038750%	11.6875038750%	273.75873203	2.66629686	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	2.66629686
IIA1	$67,648,000.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
IIA2	$22,549,333.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
IIA3	$136,786,429.00	5.0000000000%	5.0000000000%	490.70896646	2.04462067	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	2.04462067
IIA4	$54,714,571.00	2.0750000000%	2.0750000000%	490.70896636	0.84851766	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.84851766
IIA5	$54,714,571.00	6.4250000000%	6.4250000000%	490.70896636	2.62733761	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	2.62733761
IIA6	$12,368,932.00	6.0000000000%	6.0000000000%	1,000.00000000	5.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	5.00000000
IIA7	$99,116,054.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
IIA8	$24,779,014.00	17.6200000000%	0.0000000000%	0.00000040	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
IIA9	$54,750,000.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
IIA10	$2,281,250.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
IIIA1	$59,614,000.00	4.7500000000%	4.7500000000%	566.27875029	2.24152011	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	2.24152011
IIIA2	$8,129,181.00	5.5000000000%	5.5000000000%	566.27880718	2.59544473	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	2.59544473
IIIA3	$3,198,000.00	5.5000000000%	5.5000000000%	1,085.79399312	4.97655722	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.97655722
IIX	$14,924,708.00	6.0000000000%	6.0000000000%	170.17163418	0.85085819	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.85085819
IIIX	$1,392,783.00	5.5000000000%	5.5000000000%	565.95923414	2.59397911	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	2.59397911
IP	$4,774,932.00	0.0000000000%	0.0000000000%	505.37134979	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
AP	$3,195,695.58	0.0000000000%	0.0000000000%	383.35116075	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
CB1	$8,278,000.00	5.7703413037%	5.7703413037%	957.37281227	4.60363977	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.60363977
CB2	$4,357,000.00	5.7703413037%	5.7703413037%	957.37280698	4.60364012	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.60364012
CB3	$2,178,000.00	5.7703413037%	5.7703413037%	957.37280533	4.60364096	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.60364096
CB4	$871,000.00	5.7703413037%	5.7703413037%	957.37280138	4.60363949	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.60363949
CB5	$871,000.00	5.7703413037%	5.7703413037%	957.37280138	4.60363949	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.60363949
CB6	$1,308,002.51	5.7703413037%	5.7703413037%	957.37282645	4.60363795	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.60363795
R	$100.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
R_SYN	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2004 DISTRIBUTION REPORT
SERIES: WAMMS 03MS4
WEIGHTED AVERAGE PC RATE: 5.36728%
WEIGHTED AVERAGE MATURITY: 152.72903
WEIGHTED AVERAGE LOAN AGE: 23.40938
POOL NUMBER: 2051
ISSUE DATE: 02/27/2003
CERTIFICATE BALANCE AT ISSUE: $344,325,013.18
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	246		$99,998,333.62
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$449,090.94
Unscheduled Principal Collection/Reversals		$115,740.61
Liquidations-in-full	4	$1,764,852.73
Subsequent Recoveries		$0.00
Net principal Distributed		$2,329,684.28	-$2,329,684.28

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	242		$97,668,649.34

SCHEDULED INTEREST AT MORTGAGE RATE:		$480,925.81

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
Interest Uncollected on Prepayment		$0.00
Uncompensated Uncollected Interest		$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
09/2004 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$33,660.27

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:		$2,776,949.82

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2004 DISTRIBUTION REPORT
SERIES: WAMMS 03MS4
WEIGHTED AVERAGE PC RATE: 6.07216%
WEIGHTED AVERAGE MATURITY: 331.72904
WEIGHTED AVERAGE LOAN AGE: 22.96075
POOL NUMBER: 2052
ISSUE DATE: 02/27/2003
CERTIFICATE BALANCE AT ISSUE: $462,704,126.37
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	272		$116,722,742.18
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$130,301.33
Unscheduled Principal Collection/Reversals		$26,391.68
Liquidations-in-full	5	$2,108,716.92
Subsequent Recoveries		$0.00
Net principal Distributed		$2,265,409.93	-$2,265,409.93

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	267		$114,457,332.25

SCHEDULED INTEREST AT MORTGAGE RATE:		$619,812.96

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
Interest Uncollected on Prepayment		$0.00
Uncompensated Uncollected Interest		$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
09/2004 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$29,180.65

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:		$2,856,042.24

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2004 DISTRIBUTION REPORT
SERIES: WAMMS 03MS4
WEIGHTED AVERAGE PC RATE: 5.59960%
WEIGHTED AVERAGE MATURITY: 332.98781
WEIGHTED AVERAGE LOAN AGE: 22.25680
POOL NUMBER: 2053
ISSUE DATE: 02/27/2003
CERTIFICATE BALANCE AT ISSUE: $64,270,590.54
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	90		$38,611,679.52
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$45,902.66
Unscheduled Principal Collection/Reversals		$14,953.94
Liquidations-in-full	1	$338,887.49
Subsequent Recoveries		$0.00
Net principal Distributed		$399,744.09	-$399,744.09

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	89		$38,211,935.43

SCHEDULED INTEREST AT MORTGAGE RATE:		$189,827.86

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
Interest Uncollected on Prepayment		$0.00
Uncompensated Uncollected Interest		$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
09/2004 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$9,652.88

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:		$579,919.07

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2004 DISTRIBUTION REPORT
SERIES: WAMMS 03MS4
WEIGHTED AVERAGE PC RATE: 5.72464%
WEIGHTED AVERAGE MATURITY: 262.08482
WEIGHTED AVERAGE LOAN AGE: 23.02833
POOL NUMBER: Group 1
ISSUE DATE: 02/27/2003
CERTIFICATE BALANCE AT ISSUE: $871,299,730.09
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	608		$255,332,755.32
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$625,294.93
Unscheduled Principal Collection/Reversals		$157,086.23
Liquidations-in-full	10	$4,212,457.14
Subsequent Recoveries		$0.00
Net principal Distributed		$4,994,838.30	-$4,994,838.30

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	598		$250,337,917.02

SCHEDULED INTEREST AT MORTGAGE RATE:		$1,290,566.63

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
Interest Uncollected on Prepayment		$0.00
Uncompensated Uncollected Interest		$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
09/2004 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$72,493.80

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:		$6,212,911.13

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
09/2004 DISTRIBUTION REPORT
SERIES: WAMMS 03MS4
WEIGHTED AVERAGE PC RATE: 5.72464%
WEIGHTED AVERAGE MATURITY: 262.08482
WEIGHTED AVERAGE LOAN AGE: 23.02833
POOL NUMBER: ALL
ISSUE DATE: 02/27/2003
CERTIFICATE BALANCE AT ISSUE: $871,299,730.09
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	608		$255,332,755.32
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$625,294.93
Unscheduled Principal Collection/Reversals		$157,086.23
Liquidations-in-full	10	$4,212,457.14
Subsequent Recoveries		$0.00
Net principal Distributed		$4,994,838.30	-$4,994,838.30

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	598		$250,337,917.02

SCHEDULED INTEREST AT MORTGAGE RATE:		$1,290,566.63

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
Interest Uncollected on Prepayment		$0.00
Uncompensated Uncollected Interest		$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
09/2004 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$72,493.80

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:		$6,212,911.13

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03MS4
Distribution Date: 09/27/2004

Distribution by Group
Pool ID		Principal		Interest		Total
Pool - 2051		$2,329,684.28		$447,265.54		$2,776,949.82
Pool - 2052		$2,265,409.93		$590,632.31		$2,856,042.24
Pool - 2053		$399,744.09		$180,174.98		$579,919.07
Group 1		$4,994,838.30		$1,218,072.83		$6,212,911.13
Aggregate		$4,994,838.30		$1,218,072.83		$6,212,911.13

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
Pool - 2051	$99,998,333.62	246	4	242	$97,668,649.34	$449,090.94	$1,764,852.73	$115,740.61	$2,329,684.28
Pool - 2052	$116,722,742.18	272	5	267	$114,457,332.25	$130,301.33	$2,108,716.92	$26,391.68	$2,265,409.93
Pool - 2053	$38,611,679.52	90	1	89	$38,211,935.43	$45,902.66	$338,887.49	$14,953.94	$399,744.09
Group 1	$255,332,755.32	608	10	598	$250,337,917.02	$625,294.93	$4,212,457.14	$157,086.23	$4,994,838.30
Aggregate	$255,332,755.32	608	10	598	$250,337,917.02	$625,294.93	$4,212,457.14	$157,086.23	$4,994,838.30

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
Pool - 2051	2	$851,201.91	0	$0.00	0	$0.00	0	$0.00
Pool - 2052	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Pool - 2053	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Group 1	2	$851,201.91	0	$0.00	0	$0.00	0	$0.00
Aggregate	2	$851,201.91	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
Pool - 2051		0		$0.00		0		$0.00
Pool - 2052		0		$0.00		0		$0.00
Pool - 2053		0		$0.00		0		$0.00
Group 1		0		$0.00		0		$0.00
Aggregate		0		$0.00		0		$0.00

Aggregate Loss Amounts by Group
Pool ID			Count			Loss Amount
Pool - 2051			0			$0.00
Pool - 2052			0			$0.00
Pool - 2053			0			$0.00
Group 1			0			$0.00
Aggregate			0			$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03MS4
Distribution Date: 09/27/2004

INSURANCE RESERVES - Group 1
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	$8,712,997.00	$0.00	$0.00	$0.00	$8,712,997.00
Bankruptcy Bond
Single-Units	$130,190.00	$0.00	$0.00	$0.00	$130,190.00
Multi-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Mortgage Repurchase	$8,712,997.00	$0.00	$0.00	$0.00	$8,712,997.00

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	$8,712,997.00	$0.00	$0.00	$0.00	$8,712,997.00
Bankruptcy Bond
Single-Units	$130,190.00	$0.00	$0.00	$0.00	$130,190.00
Multi-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Mortgage Repurchase	$8,712,997.00	$0.00	$0.00	$0.00	$8,712,997.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMMS.03MS4
Distribution Date: 09/27/2004

The Group C-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, and III Certificates. The "Prospectus Supplement" is that certain Prospectus Supplement, dated February 25, 2003 to that certain Prospectus Supplement, dated November 21, 2002, to which certain Group I,II, and III Certificates were offered. The Special Hazard, Bankruptcy, and Fraud coverage (collectively, "Credit Enhancements") provided by the C-B certificates provide coverage to the Group I,II, and III Loans, subject to the conditions and limitations to payment specified thereunder.



The Class Principal Balances of each Class of the Class CB1,CB2,CB3,CB4,CB5,CB6 Certificatesimmediately after the principal and interest distribution on 200409 are as follows:

Class			Class Principal Balance
CB1			$7,905,981.23
CB2			$4,161,193.53
CB3			$2,080,119.23
CB4			$831,856.68
CB5			$831,856.68
CB6			$1,249,220.04
Total			$17,060,227.38
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 $8,712,997.00, $130,190.00, $8,712,997.00 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 MSC MORT PASS THRU CERT SERIES 2003-MS4 8-K