BACKGROUND: The emergence of specialty hospitals focusing on narrow procedural areas has generated controversy, although little is known about their quality. METHODS: We conducted a retrospective cohort study of 42,737 Medicare beneficiaries who underwent percutaneous coronary intervention(PCI) and 26,274 who underwent coronary-artery bypass grafting(CABG) during 2000 and 2001 in specialty cardiac hospitals(15 for PCI and 15 for CABG) and general hospitals(82 for PCI and 75 for CABG) in the same markets. Administrative data were used to compare patients’characteristics, hospital procedural volumes, and patient outcomes. RESULTS: Patients undergoing PCI or CABG in specialty hospitals were less likely to have coexisting conditions than those being treated at general hospitals and were less likely to have had an acute myocardial infarction(P< 0.001). The better health of the patients at specialty hospitals than of those at general hospitals was reflected by the lower mean predicted risk of death(2.1 percent vs. 3.1 percent for PCI and 5.0 percent vs. 5.8 percent for CABG; P< 0.001 for each comparison). Mean volumes of PCI and CABG procedures in 2000 and 2001 were higher in specialty hospitals than in general hospitals(799 vs. 375 PCI procedures, P< 0.001; and 571 vs. 236 CABG procedures, P< 0.001). The unadjusted rate of death during the index hospitalization or within 30 days after admission was lower in specialty hospitals than in general hospitals(2.1 percent vs. 3.2 percent for PCI and 4.7 percent vs. 6.0 percent for CABG; P< 0.001 for both comparisons). In multivariate analyses adjusted for patients’characteristics, the odds ratio for death after PCI in specialty hospitals and general hospitals was similar(0.89; 95 percent confidence interval, 0.69 to 1.15; P=0.39), but the odds ratio for death after CABG was lower in specialty hospitals than in general hospitals(0.84; 95 percent confidence interval, 0.72 to 0.99; P=0.05). In stratified analyses comparing specialty and general hospitals with similar volumes, differences in mortality were not significant. CONCLUSIONS: The lower unadjusted mortality rate after cardiac revascularization in specialty cardiac hospitals is accounted for by their healthier patients and higher procedural volumes. METHODS: We conducted a retrospective cohort study of 42,737 Medicare beneficiaries who underwent percutaneous coronary intervention (PCI) and 26,274 who underwent coronary- artery bypass grafting (CABG) during 2000 and 2001 in specialty cardiac hospitals (15 for PCI and 15 for CABG) and general hospitals (82 for PCI and 75 for CABG) in the same markets. Administrative data were used to compare patients’ characteristics, hospital procedural volumes, and patient outcomes. RESULTS: Patients undergoing PCI or CABG in specialty hospitals were less likely to have coexisting conditions than those being treated at general hospitals and were less likely to have had an acute myocardial infarction (P <0.001). The better health of the patients at specialty hospitals than of those at general hospitals was reflected by the lower mean predicted risk o Mean volumes of PCI and CABG procedures in 2000 and 2001 were higher in specialty hospitals than in general hospitals (p <0.001 for each comparison) 799 vs. 375 PCI procedures, P <0.001; and 571 vs. 236 CABG procedures, P <0.001). The unadjusted rate of death during the index hospitalization or within 30 days after admission was lower in specialty hospitals than in general hospitals (2.1 percent vs. 3.2 percent for PCI and 4.7 percent vs. 6.0 percent for CABG; P <0.001 for both comparisons. In multivariate analyzes adjusted for patients’characteristics, the odds ratio for death after PCI in specialty hospitals and general hospitals was similar ( 0.89; 95 percent confidence interval, 0.69 to 1.15; P = 0.39), but the odds ratio for death after CABG was lower in specialty hospitals than in general hospitals (0.84; 95 percent confidence interval, 0.72 to 0.99; In stratified analyzes comparing specialty and general hospitals with similar volumes, differences in mortality were not significant. CONCLUSIONS: The lower unadjusted mortality rate after cardiac revascularization in specialty cardiac hospitals is accounted for by their healthier patients and higher procedural volumes.