All 7157 patients (55% men) admitted to the emergency room with chest pain or other symptoms indicative of acute myocardial infarction during a period of 21 months were registered consecutively. Chest pain was reported by 93% of the patients. On the basis of history, clinical examination, and electrocardiogram in the emergency room, all patients were prospectively classified in one of four categories: (i) obvious infarction (4% of all patients); (ii) strongly suspected infarction (20%); (iii) vague suspicion of infarction (35%); and (iv) no suspected infarction (41%). In patients with no suspected infarction (n = 2910), musculoskeletal (26%), obscure (21%) and psychogenic origins (16%) of the symptoms occurred most frequently. We conclude that few of the patients had an obvious infarction on admission, and that a musculoskeletal origin of the symptoms occurred most frequently in patients with no suspected infarction.