Context: Certificate of need regulations were enacted to control health care costs by limiting unnecessary expansion of services. While many states have repealed certificate of need regulations in recent years, few analyses have examined relationships between certificate of need regulations and outcomes of care. Objective: To compare rates of coronary revascularization and mortality after acute myocardial infarction in states with and without certificate of need regulations. Design, Setting, and Participants: Retrospective cohort study of 1 139 792 Medicare beneficiaries aged 68 years or older with AMI who were admitted to 4587 US hospitals during 2000-2003. Main Outcome Measures: Thirty-day risk-adjusted rates of coronary revascularization with either coronary artery bypass graft surgery or percutaneous coronary intervention and 30-day all-cause mortality. Results: The 624 421 patients in states with certificate of need regulations were less likely to be admitted to hospitals with coronary revascularization services(321 573[51.5%] vs 323 695[62.8%]; P< .001) or to undergo revascularization at the admitting hospital(163 120[26.1%] vs 163 877[31.8%]; P< .001) than patients in states without certificates of need but were more likely to undergo revascularization at a transfer hospital(73 379[11.7%] vs 45 907[8.9%]; P< .001). Adjusting for demographic and clinical risk factors, patients in states with highly and moderately stringent certificate of need regulations, respectively, were less likely to undergo revascularization within the first 2 days(adjusted hazard ratios, 0.68; 95%confidence interval[CI], 0.54-0.87; P=.002 and 0.80; 95%CI, 0.71-0.90; P< .001) relative to patients in states without certificates of need, although no differences in the likelihood of revascularization were observed during days 3 through 30. Unadjusted 30-day mortality was similar in states with and without certificates of need(109 304[17.5%] vs 90 104[17.5%]; P=.76), as was adjusted mortality(odds ratio, 1.00; 95%CI, 0.97-1.03; P=.90). Conclusions: Patients with acute myocardial infarction were less likely to be admitted to hospitals offering coronary revascularization and to undergo early revascularization in states with certificate of need regulations. However, differences in the availability and use of revascularization therapies were not associated with mortality. Context: Certificate of need regulations were enacted to control health care costs by restriction unnecessary expansion of services. While many states have repealed certificate of need regulations in recent years, few analyzes have have relationships relationships between certificate of need regulations and outcomes of care. Objective: To compare rates of coronary revascularization and mortality after acute myocardial infarction in states with and without certificate of need regulations. Design, Setting, and Participants: Retrospective cohort study of 1 139 792 Medicare beneficiaries aged 68 years or older with AMI who were admitted to 4587 US hospitals during 2000-2003. Main Outcome Measures: Thirty-day risk-adjusted rates of coronary revascularization with either coronary artery bypass graft surgery or percutaneous coronary intervention and 30-day all-cause mortality. Results: The 624 421 patients in states with certificate of need regulations were less likely to be admitted to hospitals with cor (321 573 [51.5%] vs 323 695 [62.8%]; P <.001) or to undergo revascularization at the admitting hospital (163 120 [26.1%] vs 163 877 [31.8%]; P <.001 ) than patients in states without certificates of need but were more likely to up revascularization at a transfer hospital (73 379 [11.7%] vs 45 907 [8.9%]; P <.001). Adjusting for demographic and clinical risk factors, patients in states with highly and moderately stringent certificate of need regulations, respectively, were less likely to mut revascularization within the first 2 days (adjusted hazard ratios, 0.68; 95% confidence interval [CI], 0.54-0.87; P = .002 and 0.80 ; 95% CI, 0.71-0.90; P <.001) relative to patients in states without certificates of need, although no differences in the likelihood of revascularization were observed during days 3 through 30. Unadjusted 30-day mortality was similar in states with and without certificates of need (109 304 [17.5%] vs 90 104 [17.5%]; P = .76), as was adjusted mortalitConclusions: Patients with acute myocardial infarction were less likely to be admitted to hospitals Offering coronary revascularization and for prior early revascularization in states with certificate of need regulations. However, differences in the availability and use of revascularization therapies were not associated with mortality.