Symptomatic myocardial infarction without chest pain was identified in 26 of 102 patients (25.5%) admitted to the hospital with acute myocardial infarction. As a group, these patients had a significantly lesser prevalence of a history of angina (P less than 0.05) and cigarette smoking (P less than 0.01). Their mean age was 69.1 years compared with 58.7 years for patients with chest pain (P less than 0.001). The group had a significantly greater median delay between the onset of symptoms and (1) arrival at the hospital (P less than 0.05), (2) examination by a physician in the emergency room (P less than 0.05), (3) diagnosis of possible myocardial infarction (P less than 0.001), and (4) transfer from the emergency room to the intensive care unit (P less than 0.001). They had significantly higher admission values for mean heart rate, respiratory rate, temperature and white blood cell count and more frequent in-hospital complications of pneumonia (P less than 0.001) and cardiogenic shock (P less than 0.05). Mortality in the group was 50% compared with 18% in the group with chest pain (P less than 0.05). Discriminant function analysis identified an at-risk population with 80% reliability.