WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.04RS1
Distribution Date: 12/27/2004

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
A1	92922FML9	$107,707,858.00	$93,076,399.38	4.5000000000%	4.5000000000%	$349,036.50	$1,747,009.98	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$2,096,046.48	$91,329,389.40
A2	92922FMM7	$13,963,546.00	$13,963,546.00	5.5000000000%	5.5000000000%	$63,999.59	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$63,999.59	$13,963,546.00
A3	92922FMN5	$15,000,000.00	$15,000,000.00	5.5000000000%	5.5000000000%	$68,750.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$68,750.00	$15,000,000.00
A4	92922FMP0	$36,750,000.00	$36,750,000.00	5.5000000000%	5.5000000000%	$168,437.50	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$168,437.50	$36,750,000.00
A5	92922FMQ8	$4,587,000.00	$4,587,000.00	5.5000000000%	5.5000000000%	$21,023.75	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$21,023.75	$4,587,000.00
A6	92922FMR6	$245,454.00	$245,454.00	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	$245,454.00
A7	92922FMS4	$62,402,144.00	$53,451,932.54	4.5000000000%	4.5000000000%	$200,444.75	$1,068,663.70	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,269,108.45	$52,383,268.84
A8	92922FMT2	$39,960,856.00	$34,229,352.44	2.6375000000%	2.6375000000%	$75,233.26	$684,346.94	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$759,580.21	$33,545,005.50
A9	92922FMU9	$39,960,856.00	$34,229,352.44	5.3625000000%	5.3625000000%	$152,962.42	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$152,962.42	$33,545,005.50
A10	92922FMV7	$9,070,472.00	$9,070,472.00	5.5000000000%	5.5000000000%	$41,573.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$41,573.00	$9,070,472.00
A11	92922FMW5	$30,597,000.00	$30,597,000.00	5.5000000000%	5.5000000000%	$140,236.25	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$140,236.25	$30,597,000.00
A12	92922FMX3	$1,130,449.00	$1,014,668.20	0.0000000000%	0.0000000000%	$0.00	$13,824.34	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$13,824.34	$1,000,843.86
A13	92922FMY1	$43,083,142.00	$37,230,558.71	2.6875000000%	2.6875000000%	$83,380.94	$698,803.97	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$782,184.91	$36,531,754.74
A14	92922FMZ8	$43,083,142.00	$37,230,558.71	5.3125000000%	5.3125000000%	$164,822.79	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$164,822.79	$36,531,754.74
A15	92922FNA2	$23,779,000.00	$23,230,951.47	4.0000000000%	4.0000000000%	$77,436.50	$294,724.71	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$372,161.21	$22,936,226.76
A16	92922FNB0	$3,242,590.00	$3,167,857.02	5.5000000000%	5.5000000000%	$14,519.34	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$14,519.34	$3,127,667.29
A17	92922FNC8	$25,396,000.00	$19,571,746.28	4.7000000000%	4.7000000000%	$76,656.01	$561,649.45	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$638,305.46	$19,010,096.83
A18	92922FND6	$230,872.00	$177,924.97	5.5000000000%	5.5000000000%	$815.49	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$815.49	$172,819.06
A19	92922FNE4	$25,000.00	$25,904.85	4.7500000000%	4.7500000000%	$102.54	($102.54)	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$26,007.39
A20	92922FNF1	$800,000.00	$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
R	92922FNG9	$100.00	$0.00	0.0000000000%	0.0000000000%	$0.01	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.01	$0.00
ADMINFEE	XXXXXXXXX	$414,498,021.00	$372,044,985.87	0.0150000000%	0.0150000000%	$4,650.56	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$4,650.56	$366,976,065.31
A3_PREMIUM	XXXXXXXXX	$0.00	$0.00	0.0000000000%	0.0000000000%	$1,125.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,125.00	$0.00
A3_ROUND	XXXXXXXXX	$15,000,000.00	$15,000,000.00	5.5000000000%	5.5000000000%	$68,750.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$68,750.00	$15,000,000.00
Total		$414,498,021.00	$372,044,985.87			$1,705,206.19	$5,068,920.56	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$6,774,126.75	$366,976,065.31

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.04RS1
Distribution Date: 12/27/2004

Class	Orig Face	Beg Bal	Prin Loss	Prin Reimbursed	Subsequent Recoveries	Deferred Interest	Total Prin	End Cert Pct	End Cert Bal
A1	$107,707,858.00	$93,076,399.38	$0.00	$0.00	$0.00	$0.00	$1,747,009.98	0.8479361775	$91,329,389.40
A2	$13,963,546.00	$13,963,546.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$13,963,546.00
A3	$15,000,000.00	$15,000,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$15,000,000.00
A4	$36,750,000.00	$36,750,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$36,750,000.00
A5	$4,587,000.00	$4,587,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$4,587,000.00
A6	$245,454.00	$245,454.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$245,454.00
A7	$62,402,144.00	$53,451,932.54	$0.00	$0.00	$0.00	$0.00	$1,068,663.70	0.8394466197	$52,383,268.84
A8	$39,960,856.00	$34,229,352.44	$0.00	$0.00	$0.00	$0.00	$684,346.94	0.8394466200	$33,545,005.50
A9	$39,960,856.00	$34,229,352.44	$0.00	$0.00	$0.00	$0.00	$0.00	0.8394466200	$33,545,005.50
A10	$9,070,472.00	$9,070,472.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$9,070,472.00
A11	$30,597,000.00	$30,597,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$30,597,000.00
A12	$1,130,449.00	$1,014,668.20	$0.00	$0.00	$0.00	$0.00	$13,824.34	0.8853507412	$1,000,843.86
A13	$43,083,142.00	$37,230,558.71	$0.00	$0.00	$0.00	$0.00	$698,803.97	0.8479361774	$36,531,754.74
A14	$43,083,142.00	$37,230,558.71	$0.00	$0.00	$0.00	$0.00	$0.00	0.8479361774	$36,531,754.74
A15	$23,779,000.00	$23,230,951.47	$0.00	$0.00	$0.00	$0.00	$294,724.71	0.9645580874	$22,936,226.76
A16	$3,242,590.00	$3,167,857.02	$0.00	$0.00	$0.00	$0.00	$0.00	0.9645583592	$3,127,667.29
A17	$25,396,000.00	$19,571,746.28	$0.00	$0.00	$0.00	$0.00	$561,649.45	0.7485468905	$19,010,096.83
A18	$230,872.00	$177,924.97	$0.00	$0.00	$0.00	$0.00	$0.00	0.7485492394	$172,819.06
A19	$25,000.00	$25,904.85	$0.00	$0.00	$0.00	$0.00	($102.54)	1.0402956000	$26,007.39
A20	$800,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
R	$100.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
ADMINFEE	$414,498,021.00	$372,044,985.87	$0.00	$0.00	$0.00	$0.00	$0.00	0.8853505848	$366,976,065.31
A3_PREMIUM	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	0.0000000000	$0.00
A3_ROUND	$15,000,000.00	$15,000,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$15,000,000.00
Total	$414,498,021.00	$372,044,985.87	$0.00	$0.00	$0.00	$0.00	$5,068,920.56	0.8853505848	$366,976,065.31

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.04RS1
Distribution Date: 12/27/2004
PER $1000 DENOMINATION
Class	Orig Face	Beg Bal	Prin Loss	Prin Reimbursed	Subsequent Recoveries	Deferred Interest	Total Prin	End Cert Pct	End Cert Bal
A1	$107,707,858.00	864.15607095	0.00000000	0.00000000	0.00000000	0.00000000	16.21989345	0.8479361775	847.93617751
A2	$13,963,546.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
A3	$15,000,000.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
A4	$36,750,000.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
A5	$4,587,000.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
A6	$245,454.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
A7	$62,402,144.00	856.57205208	0.00000000	0.00000000	0.00000000	0.00000000	17.12543242	0.8394466197	839.44661965
A8	$39,960,856.00	856.57205241	0.00000000	0.00000000	0.00000000	0.00000000	17.12543245	0.8394466200	839.44661996
A9	$39,960,856.00	856.57205241	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.8394466200	839.44661996
A10	$9,070,472.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
A11	$30,597,000.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
A12	$1,130,449.00	897.57981121	0.00000000	0.00000000	0.00000000	0.00000000	12.22907004	0.8853507412	885.35074117
A13	$43,083,142.00	864.15607084	0.00000000	0.00000000	0.00000000	0.00000000	16.21989339	0.8479361774	847.93617745
A14	$43,083,142.00	864.15607084	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.8479361774	847.93617745
A15	$23,779,000.00	976.95241474	0.00000000	0.00000000	0.00000000	0.00000000	12.39432735	0.9645580874	964.55808739
A16	$3,242,590.00	976.95268905	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.9645583592	964.55835921
A17	$25,396,000.00	770.66255631	0.00000000	0.00000000	0.00000000	0.00000000	22.11566585	0.7485468905	748.54689046
A18	$230,872.00	770.66500052	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.7485492394	748.54923941
A19	$25,000.00	1,036.19400000	0.00000000	0.00000000	0.00000000	0.00000000	-4.10160000	1.0402956000	1,040.29560000
A20	$800,000.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
R	$100.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
ADMINFEE	$414,498,021.00	897.57964338	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.8853505848	885.35058485
A3_PREMIUM	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
A3_ROUND	$15,000,000.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.04RS1
Distribution Date: 12/27/2004

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
A1	$107,707,858.00	4.5000000000%	4.5000000000%	$93,076,399.38	$349,036.50	$0.00	$0.00	$0.00	$0.00	$0.00	$349,036.50
A2	$13,963,546.00	5.5000000000%	5.5000000000%	$13,963,546.00	$63,999.59	$0.00	$0.00	$0.00	$0.00	$0.00	$63,999.59
A3	$15,000,000.00	5.5000000000%	5.5000000000%	$15,000,000.00	$68,750.00	$0.00	$0.00	$0.00	$0.00	$0.00	$68,750.00
A4	$36,750,000.00	5.5000000000%	5.5000000000%	$36,750,000.00	$168,437.50	$0.00	$0.00	$0.00	$0.00	$0.00	$168,437.50
A5	$4,587,000.00	5.5000000000%	5.5000000000%	$4,587,000.00	$21,023.75	$0.00	$0.00	$0.00	$0.00	$0.00	$21,023.75
A6	$245,454.00	0.0000000000%	0.0000000000%	$245,454.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
A7	$62,402,144.00	4.5000000000%	4.5000000000%	$53,451,932.54	$200,444.75	$0.00	$0.00	$0.00	$0.00	$0.00	$200,444.75
A8	$39,960,856.00	2.6375000000%	2.6375000000%	$34,229,352.44	$75,233.26	$0.00	$0.00	$0.00	$0.00	$0.00	$75,233.26
A9	$39,960,856.00	5.3625000000%	5.3625000000%	$34,229,352.44	$152,962.42	$0.00	$0.00	$0.00	$0.00	$0.00	$152,962.42
A10	$9,070,472.00	5.5000000000%	5.5000000000%	$9,070,472.00	$41,573.00	$0.00	$0.00	$0.00	$0.00	$0.00	$41,573.00
A11	$30,597,000.00	5.5000000000%	5.5000000000%	$30,597,000.00	$140,236.25	$0.00	$0.00	$0.00	$0.00	$0.00	$140,236.25
A12	$1,130,449.00	0.0000000000%	0.0000000000%	$1,014,668.20	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
A13	$43,083,142.00	2.6875000000%	2.6875000000%	$37,230,558.71	$83,380.94	$0.00	$0.00	$0.00	$0.00	$0.00	$83,380.94
A14	$43,083,142.00	5.3125000000%	5.3125000000%	$37,230,558.71	$164,822.79	$0.00	$0.00	$0.00	$0.00	$0.00	$164,822.79
A15	$23,779,000.00	4.0000000000%	4.0000000000%	$23,230,951.47	$77,436.50	$0.00	$0.00	$0.00	$0.00	$0.00	$77,436.50
A16	$3,242,590.00	5.5000000000%	5.5000000000%	$3,167,857.02	$14,519.34	$0.00	$0.00	$0.00	$0.00	$0.00	$14,519.34
A17	$25,396,000.00	4.7000000000%	4.7000000000%	$19,571,746.28	$76,656.01	$0.00	$0.00	$0.00	$0.00	$0.00	$76,656.01
A18	$230,872.00	5.5000000000%	5.5000000000%	$177,924.97	$815.49	$0.00	$0.00	$0.00	$0.00	$0.00	$815.49
A19	$25,000.00	4.7500000000%	4.7500000000%	$25,904.85	$102.54	$0.00	$0.00	$0.00	$0.00	$0.00	$102.54
A20	$800,000.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
R	$100.00	0.0000000000%	0.0000000000%	$0.00	$0.01	$0.00	$0.00	$0.00	$0.00	$0.00	$0.01
ADMINFEE	$414,498,021.00	0.0150000000%	0.0150000000%	$372,044,985.87	$4,650.56	$0.00	$0.00	$0.00	$0.00	$0.00	$4,650.56
A3_PREMIUM	$0.00	0.0000000000%	0.0000000000%	$0.00	$1,125.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,125.00
A3_ROUND	$15,000,000.00	5.5000000000%	5.5000000000%	$15,000,000.00	$68,750.00	$0.00	$0.00	$0.00	$0.00	$0.00	$68,750.00
Total	$414,498,021.00			$372,044,985.87	$1,705,206.19	$0.00	$0.00	$0.00	$0.00	$0.00	$1,705,206.19

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.04RS1
Distribution Date: 12/27/2004
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
A1	$107,707,858.00	4.5000000000%	4.5000000000%	864.15607095	3.24058529	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.24058529
A2	$13,963,546.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333363	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333363
A3	$15,000,000.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333333	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333333
A4	$36,750,000.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333333	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333333
A5	$4,587,000.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333333	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333333
A6	$245,454.00	0.0000000000%	0.0000000000%	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
A7	$62,402,144.00	4.5000000000%	4.5000000000%	856.57205208	3.21214524	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.21214524
A8	$39,960,856.00	2.6375000000%	2.6375000000%	856.57205241	1.88267388	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.88267388
A9	$39,960,856.00	5.3625000000%	5.3625000000%	856.57205241	3.82780639	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.82780639
A10	$9,070,472.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333370	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333370
A11	$30,597,000.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333333	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333333
A12	$1,130,449.00	0.0000000000%	0.0000000000%	897.57981121	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
A13	$43,083,142.00	2.6875000000%	2.6875000000%	864.15607084	1.93534956	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.93534956
A14	$43,083,142.00	5.3125000000%	5.3125000000%	864.15607084	3.82569103	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.82569103
A15	$23,779,000.00	4.0000000000%	4.0000000000%	976.95241474	3.25650784	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.25650784
A16	$3,242,590.00	5.5000000000%	5.5000000000%	976.95268905	4.47769838	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.47769838
A17	$25,396,000.00	4.7000000000%	4.7000000000%	770.66255631	3.01842849	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.01842849
A18	$230,872.00	5.5000000000%	5.5000000000%	770.66500052	3.53221699	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.53221699
A19	$25,000.00	4.7500000000%	4.7500000000%	1,036.19400000	4.10160000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.10160000
A20	$800,000.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
R	$100.00	0.0000000000%	0.0000000000%	0.00000000	0.10000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.10000000
ADMINFEE	$414,498,021.00	0.0150000000%	0.0150000000%	897.57964338	0.01121974	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.01121974
A3_PREMIUM	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
A3_ROUND	$15,000,000.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333333	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333333

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
12/2004 DISTRIBUTION REPORT
SERIES: WAMU 04RS1
WEIGHTED AVERAGE PC RATE: 0.00000%
WEIGHTED AVERAGE MATURITY: 0.00000
WEIGHTED AVERAGE LOAN AGE: 0.00000
POOL NUMBER: WAMU.03S11
ISSUE DATE: 02/26/2004
CERTIFICATE BALANCE AT ISSUE: $414,498,021.47
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	1		$372,044,986.34
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$5,068,920.56
Unscheduled Principal Collection/Reversals		$0.00
Liquidations-in-full	0	$0.00
Subsequent Recoveries		$0.00
Net principal Distributed		$5,068,920.56	-$5,068,920.56

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	1		$366,976,065.78

SCHEDULED INTEREST AT MORTGAGE RATE:		$1,705,206.19

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
12/2004 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$0.00

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:		$6,774,126.75

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
12/2004 DISTRIBUTION REPORT
SERIES: WAMU 04RS1
WEIGHTED AVERAGE PC RATE: 0.00000%
WEIGHTED AVERAGE MATURITY: 0.00000
WEIGHTED AVERAGE LOAN AGE: 0.00000
POOL NUMBER: ALL
ISSUE DATE: 02/26/2004
CERTIFICATE BALANCE AT ISSUE: $414,498,021.47
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	1		$372,044,986.34
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$5,068,920.56
Unscheduled Principal Collection/Reversals		$0.00
Liquidations-in-full	0	$0.00
Subsequent Recoveries		$0.00
Net principal Distributed		$5,068,920.56	-$5,068,920.56

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	1		$366,976,065.78

SCHEDULED INTEREST AT MORTGAGE RATE:		$1,705,206.19

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
12/2004 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$0.00

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:		$6,774,126.75

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.04RS1
Distribution Date: 12/27/2004

Distribution by Group
Pool ID		Principal		Interest		Total
Pool - WAMU.03S11		$5,068,920.56		$1,705,206.19		$6,774,126.75
Aggregate		$5,068,920.56		$1,705,206.19		$6,774,126.75

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 - WAMU.03S11	$372,044,986.34	1	0	1	$366,976,065.78	$5,068,920.56	$0.00	$0.00	$5,068,920.56
Aggregate	$372,044,986.34	1	0	1	$366,976,065.78	$5,068,920.56	$0.00	$0.00	$5,068,920.56

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 - WAMU.03S11	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
Pool - WAMU.03S11		0		$0.00		0		$0.00
Aggregate		0		$0.00		0		$0.00

Aggregate Loss Amounts by Group
Pool ID			Count			Loss Amount
Pool - WAMU.03S11			0			$0.00
Aggregate			0			$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.04RS1
Distribution Date: 12/27/2004

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	$0.00	$0.00	$0.00	$0.00	$0.00
Bankruptcy Bond
Single-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Multi-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Mortgage Repurchase	$0.00	$0.00	$0.00	$0.00	$0.00

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	$0.00	$0.00	$0.00	$0.00	$0.00
Bankruptcy Bond
Single-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Multi-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Mortgage Repurchase	$0.00	$0.00	$0.00	$0.00	$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.04RS1
Distribution Date: 12/27/2004

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP SERIES 2004-RS1 8-K