The Colorado Rockies allowed the most runs by a team in May 2004, with 176 runs.

	TEAM	R	MONTH	G	W%	W	L	ERA	SO	SHO	SV	IP	H	ER	HR	BB	HBP	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Rockies	176	May 2004	29	.345	10	19	5.96	193	0	5	259.2	305	172	32	131	14	20	1,194	18	6.69	4.54	1.47	1.11	16.2	11.0	1.68	.331	6.10	10.57
2	Orioles	163	May 2004	26	.462	12	14	5.98	175	1	6	233.1	273	155	26	123	19	7	1,086	11	6.75	4.74	1.42	1.00	16.1	11.3	1.70	.332	6.29	10.53
3	Red Sox	158	May 2004	30	.533	16	14	4.55	191	0	5	265.0	278	134	23	76	15	5	1,147	2	6.49	2.58	2.51	0.78	16.7	6.6	1.34	.303	5.37	9.44
4	Diamondbacks	158	May 2004	29	.310	9	20	5.01	183	1	5	260.1	256	145	28	121	10	17	1,142	9	6.33	4.18	1.51	0.97	16.0	10.6	1.45	.285	5.46	8.85
5	Royals	153	May 2004	27	.370	10	17	5.11	134	0	6	237.2	291	135	43	89	9	5	1,077	7	5.07	3.37	1.51	1.63	12.4	8.3	1.60	.309	5.79	11.02
6	Devil Rays	151	May 2004	28	.393	11	17	5.03	160	0	7	245.0	242	137	44	111	18	5	1,092	11	5.88	4.08	1.44	1.62	14.7	10.2	1.44	.261	5.55	8.89
7	Tigers	145	May 2004	27	.407	11	16	4.92	176	0	6	241.1	251	132	31	99	9	7	1,055	12	6.56	3.69	1.78	1.16	16.7	9.4	1.45	.297	5.41	9.36
8	Pirates	141	May 2004	26	.500	13	13	4.56	180	0	6	241.0	267	122	28	102	11	19	1,072	4	6.72	3.81	1.76	1.05	16.8	9.5	1.53	.318	5.27	9.97
9	Indians	140	May 2004	26	.500	13	13	4.89	165	0	3	237.1	261	129	27	95	4	10	1,045	6	6.26	3.60	1.74	1.02	15.8	9.1	1.50	.310	5.31	9.90
10	Twins	136	May 2004	28	.429	12	16	4.34	179	0	8	257.1	285	124	26	95	7	7	1,131	5	6.26	3.32	1.88	0.91	15.8	8.4	1.48	.314	4.76	9.97
11	Rangers	135	May 2004	27	.519	14	13	4.78	165	1	9	237.0	261	126	37	80	18	1	1,037	5	6.27	3.04	2.06	1.41	15.9	7.7	1.44	.304	5.13	9.91
12	Blue Jays	132	May 2004	29	.517	15	14	4.34	204	0	7	257.1	253	124	27	108	8	8	1,110	14	7.13	3.78	1.89	0.94	18.4	9.7	1.40	.296	4.62	8.85
13	Phillies	131	May 2004	28	.607	17	11	3.86	175	1	10	254.0	266	109	33	97	10	20	1,125	8	6.20	3.44	1.80	1.17	15.6	8.6	1.43	.288	4.64	9.43
14	Yankees	130	May 2004	26	.692	18	8	4.66	137	0	10	235.2	251	122	30	60	8	10	1,010	9	5.23	2.29	2.28	1.15	13.6	5.9	1.32	.285	4.96	9.59
15	Reds	128	May 2004	29	.621	18	11	4.14	167	1	15	259.0	255	119	31	86	10	14	1,110	10	5.80	2.99	1.94	1.08	15.0	7.7	1.32	.275	4.45	8.86
16	Mariners	125	May 2004	27	.407	11	16	4.15	189	0	5	253.2	240	117	32	91	10	5	1,072	6	6.71	3.23	2.08	1.14	17.6	8.5	1.30	.277	4.43	8.52
17	Padres	123	May 2004	27	.481	13	14	4.10	197	0	8	237.0	248	108	33	88	5	4	1,037	8	7.48	3.34	2.24	1.25	19.0	8.5	1.42	.301	4.67	9.42
18	Marlins	123	May 2004	28	.536	15	13	4.09	179	0	10	253.1	241	115	33	93	7	15	1,077	6	6.36	3.30	1.92	1.17	16.6	8.6	1.32	.272	4.37	8.56
19	Mets	115	May 2004	27	.556	15	12	3.56	156	1	4	245.1	227	97	27	103	9	18	1,066	5	5.72	3.78	1.51	0.99	14.6	9.7	1.35	.259	4.22	8.33
20	Astros	114	May 2004	28	.500	14	14	3.90	251	0	5	251.2	230	109	32	91	9	12	1,067	6	8.98	3.25	2.76	1.14	23.5	8.5	1.28	.289	4.08	8.23
21	White Sox	111	May 2004	28	.571	16	12	3.78	171	0	5	247.1	261	104	25	85	5	2	1,063	6	6.22	3.09	2.01	0.91	16.1	8.0	1.40	.304	4.04	9.50
22	Athletics	111	May 2004	26	.577	15	11	3.72	173	1	4	241.2	243	100	20	93	13	12	1,039	6	6.44	3.46	1.86	0.74	16.7	9.0	1.39	.301	4.13	9.05
23	Angels	109	May 2004	27	.630	17	10	3.76	167	1	10	242.0	231	101	28	88	10	5	1,034	11	6.21	3.27	1.90	1.04	16.2	8.5	1.32	.274	4.05	8.59
24	Giants	106	May 2004	26	.615	16	10	3.45	172	1	8	240.0	228	92	26	73	9	7	1,013	9	6.45	2.74	2.36	0.97	17.0	7.2	1.25	.276	3.97	8.55
25	Cubs	105	May 2004	28	.500	14	14	3.63	209	1	6	253.0	233	102	28	78	17	10	1,066	11	7.43	2.77	2.68	1.00	19.6	7.3	1.23	.279	3.74	8.29