This study sought to evaluate the quality of care rendered to Medicare beneficiaries with acute myocardial infarction by establishing the use patterns of well-proven therapies in this population. We analyzed the quality of care rendered to 4300 Medicare beneficiaries seen at Maryland and District of Columbia hospitals with retrospectively confirmed acute myocardial infarction by evaluating the use of proven therapies. The proportion of patients ideal for therapies ranged from 10% for reperfusion to 100% for smoking cessation counseling. For ideal patients the following therapies were implemented: aspirin (87%), reperfusion therapy (64%), beta-blockers on discharge (60%), and smoking cessation counseling (41%). A substantial proportion of Medicare patients with acute myocardial infarction has one or more relative or absolute contraindications to standard regimens and therefore are not ideal therapeutic candidates. In the group of ideal patients, those with no therapeutic contraindications, a significant proportion do not receive these treatments.