Background: Prior studies have suggested that payer status may be an important determinant of medical resource utilization and outcome in acute myocardial infarction (AMI). Methods: A national cohort of 332 221 patients with AMI enrolled from June 1994 to July 1996 were compared within 5 payer groups to ascertain the influence of payer status on hospital resource allocation for AMI in the United States. Results: Medicare comprised the largest proportion (56%), followed by commercial insurance (25%), health maintenance organization (HMO) (10%), uninsured (6%), and Medicaid (3%). Compared with commercially insured patients, Medicare and Medicaid patients received fewer reperfusion therapies, underwent fewer invasive cardiac procedures, and had longer hospitalizations. After adjusting for differences in clinical characteristics, Medicare recipients were as likely as commercially insured patients to receive acute reperfusion therapies or any invasive cardiac procedure. Uninsured and HMO patients tended to utilize hospital resources with intermediate frequency. Medicare recipients aged 65 years or older and the HMO group had similar hospital mortality rates compared with the commercial group (odds ratio [OR], 1.07; 95% confidence interval [CI], 0.96-1.20 and OR, 0.93; 95% CI, 0.83-1.04, respectively), but Medicaid and uninsured groups had higher hospital mortality rates compared with the commercial group (OR, 1.30; 95% CI, 1.14-1.48 and OR, 1.29; 95% CI, 1.12-1.48, respectively). Conclusion: This report suggests significant variation by payer status in the management of AMI throughout the United States, but no important differences in mortality among the 3 largest payer groups.