WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.03S13
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
I1A1	92922FJU3	$19,500,000.00	$18,882,519.29	5.2500000000%	5.2500000000%	$82,611.02	$1,266,132.35	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,348,743.37	$17,616,386.94
I1A2	92922FJV1	$7,883,750.00	$7,883,750.00	5.2500000000%	5.2500000000%	$34,491.41	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$34,491.41	$7,883,750.00
I2A1	92922FJW9	$58,174,000.00	$43,190,981.47	5.5000000000%	5.5000000000%	$197,958.67	$551,356.14	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$749,314.81	$42,639,625.33
I2A2	92922FJX7	$50,000,000.00	$36,220,794.67	5.5000000000%	5.5000000000%	$166,011.98	$507,057.34	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$673,069.31	$35,713,737.33
I2A3	92922FJY5	$13,120,800.00	$13,120,800.00	5.5000000000%	5.5000000000%	$60,137.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$60,137.00	$13,120,800.00
I2A4	92922FJZ2	$14,500,000.00	$14,500,000.00	5.5000000000%	5.5000000000%	$66,458.33	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$66,458.33	$14,500,000.00
I2A5	92922FKA5	$15,250,000.00	$15,250,000.00	5.5000000000%	5.5000000000%	$69,895.83	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$69,895.83	$15,250,000.00
I3A1	92922FKB3	$25,177,800.00	$16,301,805.83	2.7875000000%	2.7875000000%	$37,867.74	$690,531.19	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$728,398.93	$15,611,274.64
I3A2	92922FKC1	$25,177,800.00	$16,301,805.83	5.2125000000%	5.2125000000%	$70,810.97	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$70,810.97	$15,611,274.64
IP	92922FKD9	$921,474.45	$907,014.55	0.0000000000%	0.0000000000%	$0.00	$95,793.96	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$95,793.96	$811,220.59
II1A1	92922FKE7	$90,898,200.00	$82,333,004.47	4.5000000000%	4.5000000000%	$308,748.77	$1,803,159.96	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$2,111,908.73	$80,529,844.51
II2A1	92922FKF4	$158,975,200.00	$126,527,026.54	5.0000000000%	5.0000000000%	$527,195.94	$2,425,027.63	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$2,952,223.57	$124,101,998.91
II3A1	92922FKG2	$16,162,200.00	$10,756,446.43	2.7375000000%	2.7375000000%	$24,538.14	$470,819.27	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$495,357.41	$10,285,627.16
II3A2	92922FKH0	$16,162,200.00	$10,756,446.43	5.2625000000%	5.2625000000%	$47,171.50	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$47,171.50	$10,285,627.16
IIP	92922FKJ6	$565,209.21	$534,955.98	0.0000000000%	0.0000000000%	$0.00	$2,805.93	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$2,805.93	$532,150.05
CB1	92922FKK3	$4,803,000.00	$4,650,994.55	5.3502328152%	5.3502328152%	$20,736.59	$13,260.72	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$33,997.31	$4,637,733.83
CB2	92922FKL1	$1,441,000.00	$1,395,395.20	5.3502328152%	5.3502328152%	$6,221.41	$3,978.49	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$10,199.90	$1,391,416.71
CB3	92922FKM9	$1,200,000.00	$1,162,022.37	5.3502328152%	5.3502328152%	$5,180.91	$3,313.11	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$8,494.02	$1,158,709.26
CB4	92922FJR0	$721,000.00	$698,181.78	5.3502328152%	5.3502328152%	$3,112.86	$1,990.63	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$5,103.49	$696,191.15
CB5	92922FJS8	$480,000.00	$464,808.94	5.3502328152%	5.3502328152%	$2,072.36	$1,325.24	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$3,397.61	$463,483.70
CB6	92922FJT6	$480,900.22	$465,680.65	5.3502328152%	5.3502328152%	$2,076.25	$1,327.73	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$3,403.98	$464,352.92
R	92922FKN7	$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		$480,254,633.88	$395,246,182.72			$1,733,297.67	$7,837,879.69	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$9,571,177.36	$387,408,303.03

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.03S13
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
I1A1	$19,500,000.00	$18,882,519.29	$0.00	$0.00	$0.00	$0.00	$1,266,132.35	0.9034044585	$17,616,386.94
I1A2	$7,883,750.00	$7,883,750.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$7,883,750.00
I2A1	$58,174,000.00	$43,190,981.47	$0.00	$0.00	$0.00	$0.00	$551,356.14	0.7329670528	$42,639,625.33
I2A2	$50,000,000.00	$36,220,794.67	$0.00	$0.00	$0.00	$0.00	$507,057.34	0.7142747466	$35,713,737.33
I2A3	$13,120,800.00	$13,120,800.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$13,120,800.00
I2A4	$14,500,000.00	$14,500,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$14,500,000.00
I2A5	$15,250,000.00	$15,250,000.00	$0.00	$0.00	$0.00	$0.00	$0.00	1.0000000000	$15,250,000.00
I3A1	$25,177,800.00	$16,301,805.83	$0.00	$0.00	$0.00	$0.00	$690,531.19	0.6200412522	$15,611,274.64
I3A2	$25,177,800.00	$16,301,805.83	$0.00	$0.00	$0.00	$0.00	$0.00	0.6200412522	$15,611,274.64
IP	$921,474.45	$907,014.55	$0.00	$0.00	$0.00	$0.00	$95,793.96	0.8803506055	$811,220.59
II1A1	$90,898,200.00	$82,333,004.47	$0.00	$0.00	$0.00	$0.00	$1,803,159.96	0.8859344246	$80,529,844.51
II2A1	$158,975,200.00	$126,527,026.54	$0.00	$0.00	$0.00	$0.00	$2,425,027.63	0.7806374762	$124,101,998.91
II3A1	$16,162,200.00	$10,756,446.43	$0.00	$0.00	$0.00	$0.00	$470,819.27	0.6364001906	$10,285,627.16
II3A2	$16,162,200.00	$10,756,446.43	$0.00	$0.00	$0.00	$0.00	$0.00	0.6364001906	$10,285,627.16
IIP	$565,209.21	$534,955.98	$0.00	$0.00	$0.00	$0.00	$2,805.93	0.9415098703	$532,150.05
CB1	$4,803,000.00	$4,650,994.55	$0.00	$0.00	$0.00	$0.00	$13,260.72	0.9655910535	$4,637,733.83
CB2	$1,441,000.00	$1,395,395.20	$0.00	$0.00	$0.00	$0.00	$3,978.49	0.9655910548	$1,391,416.71
CB3	$1,200,000.00	$1,162,022.37	$0.00	$0.00	$0.00	$0.00	$3,313.11	0.9655910500	$1,158,709.26
CB4	$721,000.00	$698,181.78	$0.00	$0.00	$0.00	$0.00	$1,990.63	0.9655910541	$696,191.15
CB5	$480,000.00	$464,808.94	$0.00	$0.00	$0.00	$0.00	$1,325.24	0.9655910417	$463,483.70
CB6	$480,900.22	$465,680.65	$0.00	$0.00	$0.00	$0.00	$1,327.73	0.9655909910	$464,352.92
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	$480,254,633.88	$395,246,182.72	$0.00	$0.00	$0.00	$0.00	$7,837,879.69	0.8066727017	$387,408,303.03

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.03S13
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
I1A1	$19,500,000.00	968.33432256	0.00000000	0.00000000	0.00000000	0.00000000	64.92986410	0.9034044585	903.40445846
I1A2	$7,883,750.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
I2A1	$58,174,000.00	742.44476003	0.00000000	0.00000000	0.00000000	0.00000000	9.47770722	0.7329670528	732.96705281
I2A2	$50,000,000.00	724.41589340	0.00000000	0.00000000	0.00000000	0.00000000	10.14114680	0.7142747466	714.27474660
I2A3	$13,120,800.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
I2A4	$14,500,000.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
I2A5	$15,250,000.00	1,000.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.0000000000	1,000.00000000
I3A1	$25,177,800.00	647.46744473	0.00000000	0.00000000	0.00000000	0.00000000	27.42619252	0.6200412522	620.04125221
I3A2	$25,177,800.00	647.46744473	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.6200412522	620.04125221
IP	$921,474.45	984.30786659	0.00000000	0.00000000	0.00000000	0.00000000	103.95726110	0.8803506055	880.35060549
II1A1	$90,898,200.00	905.77156060	0.00000000	0.00000000	0.00000000	0.00000000	19.83713605	0.8859344246	885.93442455
II2A1	$158,975,200.00	795.89160158	0.00000000	0.00000000	0.00000000	0.00000000	15.25412536	0.7806374762	780.63747622
II3A1	$16,162,200.00	665.53108055	0.00000000	0.00000000	0.00000000	0.00000000	29.13088998	0.6364001906	636.40019057
II3A2	$16,162,200.00	665.53108055	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.6364001906	636.40019057
IIP	$565,209.21	946.47427985	0.00000000	0.00000000	0.00000000	0.00000000	4.96440955	0.9415098703	941.50987030
CB1	$4,803,000.00	968.35197793	0.00000000	0.00000000	0.00000000	0.00000000	2.76092442	0.9655910535	965.59105351
CB2	$1,441,000.00	968.35197779	0.00000000	0.00000000	0.00000000	0.00000000	2.76092297	0.9655910548	965.59105482
CB3	$1,200,000.00	968.35197500	0.00000000	0.00000000	0.00000000	0.00000000	2.76092500	0.9655910500	965.59105000
CB4	$721,000.00	968.35198336	0.00000000	0.00000000	0.00000000	0.00000000	2.76092926	0.9655910541	965.59105409
CB5	$480,000.00	968.35195833	0.00000000	0.00000000	0.00000000	0.00000000	2.76091667	0.9655910417	965.59104167
CB6	$480,900.22	968.35191716	0.00000000	0.00000000	0.00000000	0.00000000	2.76092616	0.9655909910	965.59099100
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: WAMU.03S13
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
I1A1	$19,500,000.00	5.2500000000%	5.2500000000%	$18,882,519.29	$82,611.02	$0.00	$0.00	$0.00	$0.00	$0.00	$82,611.02
I1A2	$7,883,750.00	5.2500000000%	5.2500000000%	$7,883,750.00	$34,491.41	$0.00	$0.00	$0.00	$0.00	$0.00	$34,491.41
I2A1	$58,174,000.00	5.5000000000%	5.5000000000%	$43,190,981.47	$197,958.67	$0.00	$0.00	$0.00	$0.00	$0.00	$197,958.67
I2A2	$50,000,000.00	5.5000000000%	5.5000000000%	$36,220,794.67	$166,011.98	$0.00	$0.00	$0.00	$0.00	$0.00	$166,011.98
I2A3	$13,120,800.00	5.5000000000%	5.5000000000%	$13,120,800.00	$60,137.00	$0.00	$0.00	$0.00	$0.00	$0.00	$60,137.00
I2A4	$14,500,000.00	5.5000000000%	5.5000000000%	$14,500,000.00	$66,458.33	$0.00	$0.00	$0.00	$0.00	$0.00	$66,458.33
I2A5	$15,250,000.00	5.5000000000%	5.5000000000%	$15,250,000.00	$69,895.83	$0.00	$0.00	$0.00	$0.00	$0.00	$69,895.83
I3A1	$25,177,800.00	2.7875000000%	2.7875000000%	$16,301,805.83	$37,867.74	$0.00	$0.00	$0.00	$0.00	$0.00	$37,867.74
I3A2	$25,177,800.00	5.2125000000%	5.2125000000%	$16,301,805.83	$70,810.97	$0.00	$0.00	$0.00	$0.00	$0.00	$70,810.97
IP	$921,474.45	0.0000000000%	0.0000000000%	$907,014.55	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
II1A1	$90,898,200.00	4.5000000000%	4.5000000000%	$82,333,004.47	$308,748.77	$0.00	$0.00	$0.00	$0.00	$0.00	$308,748.77
II2A1	$158,975,200.00	5.0000000000%	5.0000000000%	$126,527,026.54	$527,195.94	$0.00	$0.00	$0.00	$0.00	$0.00	$527,195.94
II3A1	$16,162,200.00	2.7375000000%	2.7375000000%	$10,756,446.43	$24,538.14	$0.00	$0.00	$0.00	$0.00	$0.00	$24,538.14
II3A2	$16,162,200.00	5.2625000000%	5.2625000000%	$10,756,446.43	$47,171.50	$0.00	$0.00	$0.00	$0.00	$0.00	$47,171.50
IIP	$565,209.21	0.0000000000%	0.0000000000%	$534,955.98	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
CB1	$4,803,000.00	5.3502328152%	5.3502328152%	$4,650,994.55	$20,736.59	$0.00	$0.00	$0.00	$0.00	$0.00	$20,736.59
CB2	$1,441,000.00	5.3502328152%	5.3502328152%	$1,395,395.20	$6,221.41	$0.00	$0.00	$0.00	$0.00	$0.00	$6,221.41
CB3	$1,200,000.00	5.3502328152%	5.3502328152%	$1,162,022.37	$5,180.91	$0.00	$0.00	$0.00	$0.00	$0.00	$5,180.91
CB4	$721,000.00	5.3502328152%	5.3502328152%	$698,181.78	$3,112.86	$0.00	$0.00	$0.00	$0.00	$0.00	$3,112.86
CB5	$480,000.00	5.3502328152%	5.3502328152%	$464,808.94	$2,072.36	$0.00	$0.00	$0.00	$0.00	$0.00	$2,072.36
CB6	$480,900.22	5.3502328152%	5.3502328152%	$465,680.65	$2,076.25	$0.00	$0.00	$0.00	$0.00	$0.00	$2,076.25
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	$480,254,633.88			$395,246,182.72	$1,733,297.67	$0.00	$0.00	$0.00	$0.00	$0.00	$1,733,297.67

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.03S13
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
I1A1	$19,500,000.00	5.2500000000%	5.2500000000%	968.33432256	4.23646256	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.23646256
I1A2	$7,883,750.00	5.2500000000%	5.2500000000%	1,000.00000000	4.37500048	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.37500048
I2A1	$58,174,000.00	5.5000000000%	5.5000000000%	742.44476003	3.40287190	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.40287190
I2A2	$50,000,000.00	5.5000000000%	5.5000000000%	724.41589340	3.32023960	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.32023960
I2A3	$13,120,800.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333333	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333333
I2A4	$14,500,000.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333310	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333310
I2A5	$15,250,000.00	5.5000000000%	5.5000000000%	1,000.00000000	4.58333311	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.58333311
I3A1	$25,177,800.00	2.7875000000%	2.7875000000%	647.46744473	1.50401306	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.50401306
I3A2	$25,177,800.00	5.2125000000%	5.2125000000%	647.46744473	2.81243675	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	2.81243675
IP	$921,474.45	0.0000000000%	0.0000000000%	984.30786659	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
II1A1	$90,898,200.00	4.5000000000%	4.5000000000%	905.77156060	3.39664339	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.39664339
II2A1	$158,975,200.00	5.0000000000%	5.0000000000%	795.89160158	3.31621498	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	3.31621498
II3A1	$16,162,200.00	2.7375000000%	2.7375000000%	665.53108055	1.51824257	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	1.51824257
II3A2	$16,162,200.00	5.2625000000%	5.2625000000%	665.53108055	2.91863113	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	2.91863113
IIP	$565,209.21	0.0000000000%	0.0000000000%	946.47427985	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
CB1	$4,803,000.00	5.3502328152%	5.3502328152%	968.35197793	4.31742453	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.31742453
CB2	$1,441,000.00	5.3502328152%	5.3502328152%	968.35197779	4.31742540	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.31742540
CB3	$1,200,000.00	5.3502328152%	5.3502328152%	968.35197500	4.31742500	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.31742500
CB4	$721,000.00	5.3502328152%	5.3502328152%	968.35198336	4.31742025	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.31742025
CB5	$480,000.00	5.3502328152%	5.3502328152%	968.35195833	4.31741667	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.31741667
CB6	$480,900.22	5.3502328152%	5.3502328152%	968.35191716	4.31742369	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.31742369
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
12/2004 DISTRIBUTION REPORT
SERIES: WAMU 03S13
WEIGHTED AVERAGE PC RATE: 4.94885%
WEIGHTED AVERAGE MATURITY: 163.67053
WEIGHTED AVERAGE LOAN AGE: 13.90009
POOL NUMBER: 2258
ISSUE DATE: 11/24/2003
CERTIFICATE BALANCE AT ISSUE: $271,765,050.95
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	466		$225,077,542.31
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$950,066.25
Unscheduled Principal Collection/Reversals		$411,707.17
Liquidations-in-full	7	$3,360,789.54
Subsequent Recoveries		$0.00
Net principal Distributed		$4,722,562.96	-$4,722,562.96

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	459		$220,354,979.35

SCHEDULED INTEREST AT MORTGAGE RATE:		$975,120.96

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
12/2004 DISTRIBUTION REPORT
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
SCHEDULED SERVICING FEE EXPENSES:		$46,891.19

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:		$5,650,792.73

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
12/2004 DISTRIBUTION REPORT
SERIES: WAMU 03S13
WEIGHTED AVERAGE PC RATE: 5.67720%
WEIGHTED AVERAGE MATURITY: 342.20577
WEIGHTED AVERAGE LOAN AGE: 13.63764
POOL NUMBER: 2259
ISSUE DATE: 11/24/2003
CERTIFICATE BALANCE AT ISSUE: $208,489,582.93
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	357		$170,168,640.42
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$194,709.94
Unscheduled Principal Collection/Reversals		$27,846.32
Liquidations-in-full	7	$2,892,760.47
Subsequent Recoveries		$0.00
Net principal Distributed		$3,115,316.73	-$3,115,316.73

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	350		$167,053,323.69

SCHEDULED INTEREST AT MORTGAGE RATE:		$840,519.69

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:		$35,451.89

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:		$3,920,384.53

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
12/2004 DISTRIBUTION REPORT
SERIES: WAMU 03S13
WEIGHTED AVERAGE PC RATE: 5.26243%
WEIGHTED AVERAGE MATURITY: 240.65624
WEIGHTED AVERAGE LOAN AGE: 13.78692
POOL NUMBER: Group 1
ISSUE DATE: 11/24/2003
CERTIFICATE BALANCE AT ISSUE: $480,254,633.88
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	823		$395,246,182.73
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$1,144,776.19
Unscheduled Principal Collection/Reversals		$439,553.49
Liquidations-in-full	14	$6,253,550.01
Subsequent Recoveries		$0.00
Net principal Distributed		$7,837,879.69	-$7,837,879.69

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	809		$387,408,303.04

SCHEDULED INTEREST AT MORTGAGE RATE:		$1,815,640.65

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:		$82,343.08

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:		$9,571,177.26

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
MASTER SERVICING
MORTGAGE PASS-THROUGH CERTIFICATES
12/2004 DISTRIBUTION REPORT
SERIES: WAMU 03S13
WEIGHTED AVERAGE PC RATE: 5.26243%
WEIGHTED AVERAGE MATURITY: 240.65624
WEIGHTED AVERAGE LOAN AGE: 13.78692
POOL NUMBER: ALL
ISSUE DATE: 11/24/2003
CERTIFICATE BALANCE AT ISSUE: $480,254,633.88
	TOTAL NUMBER OF MORTAGES	CERTIFICATE ACCOUNT ACTIVITY (@ PCRATE)	CERTIFICATE BALANCE OUTSTANDING
BALANCES FROM LAST FISCAL MONTH-END:	823		$395,246,182.73
PRINCIPAL POOL COLLECTION(S):
Scheduled Principal Collection Due Current Month		$1,144,776.19
Unscheduled Principal Collection/Reversals		$439,553.49
Liquidations-in-full	14	$6,253,550.01
Subsequent Recoveries		$0.00
Net principal Distributed		$7,837,879.69	-$7,837,879.69

CAPITAL LOSS (PRINCIPAL WRITTEN OFF):			$0.00

BALANCE CURRENT FISCAL MONTH-END:	809		$387,408,303.04

SCHEDULED INTEREST AT MORTGAGE RATE:		$1,815,640.65

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:		$82,343.08

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:		$9,571,177.26

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.03S13
Distribution Date: 12/27/2004

Distribution by Group
Pool ID		Principal		Interest		Total
Pool - 2258		$4,722,562.96		$928,229.77		$5,650,792.73
Pool - 2259		$3,115,316.73		$805,067.80		$3,920,384.53
Group 1		$7,837,879.69		$1,733,297.57		$9,571,177.26
Aggregate		$7,837,879.69		$1,733,297.57		$9,571,177.26

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 - 2258	$225,077,542.31	466	7	459	$220,354,979.35	$950,066.25	$3,360,789.54	$411,707.17	$4,722,562.96
Pool - 2259	$170,168,640.42	357	7	350	$167,053,323.69	$194,709.94	$2,892,760.47	$27,846.32	$3,115,316.73
Group 1	$395,246,182.73	823	14	809	$387,408,303.04	$1,144,776.19	$6,253,550.01	$439,553.49	$7,837,879.69
Aggregate	$395,246,182.73	823	14	809	$387,408,303.04	$1,144,776.19	$6,253,550.01	$439,553.49	$7,837,879.69

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 - 2258	2	$692,730.62	0	$0.00	0	$0.00	0	$0.00
Pool - 2259	2	$1,514,268.96	0	$0.00	0	$0.00	0	$0.00
Group 1	4	$2,206,999.58	0	$0.00	0	$0.00	0	$0.00
Aggregate	4	$2,206,999.58	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 - 2258		0		$0.00		0		$0.00
Pool - 2259		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 - 2258			0			$0.00
Pool - 2259			0			$0.00
Group 1			0			$0.00
Aggregate			0			$0.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.03S13
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	$5,658,222.00	$0.00	$0.00	$0.00	$5,658,222.00
Bankruptcy Bond
Single-Units	$100,000.00	$0.00	$0.00	$0.00	$100,000.00
Multi-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Mortgage Repurchase	$4,802,546.00	$0.00	$0.00	$0.00	$4,802,546.00

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	$5,658,222.00	$0.00	$0.00	$0.00	$5,658,222.00
Bankruptcy Bond
Single-Units	$100,000.00	$0.00	$0.00	$0.00	$100,000.00
Multi-Units	$0.00	$0.00	$0.00	$0.00	$0.00
Mortgage Repurchase	$4,802,546.00	$0.00	$0.00	$0.00	$4,802,546.00

WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
Series: WAMU.03S13
Distribution Date: 12/27/2004

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 Senior Certificates. The "Prospectus Supplement" is that certain Prospectus Supplement, dated November 20,2003 to that certain Prospectus Supplement, dated September 19,2003, to which certain certificates were offered. The special hazard, bankruptcy, and Fraud coverage (collectively, "Credit Enhancements") provided by the C-B certificates provide coverage to the 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 200412 are as follows:

Class			Class Principal Balance
CB1			$4,637,733.83
CB2			$1,391,416.71
CB3			$1,158,709.26
CB4			$696,191.15
CB5			$463,483.70
CB6			$464,352.92
Total			$8,811,887.57
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 $5,658,222.00, $100,000.00, $4,802,546.00 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 MORT SEC CORP WAMU MO PS TH CE SE 03 S13 8-K