Previous studies have compared the outcome between patients with and without a confirmed acute myocardial infarction (AMI) mainly during the first few years after its onset. Our aim was to compare the prognosis between patients with and without a confirmed AMI during 10 years of follow-up. Patients participating in an early intervention trial with metoprolol in suspected AMI between 1976 and 1981 took part in this evaluation. The total 10-year mortality rate including hospital mortality was 51% for patients with confirmed AMI as compared with 32% for patients with a possible AMI and 23% for patients in whom AMI was definitely ruled out (p < 0.001). The 10-year mortality after discharge from hospital was in AMI 46%, possible AMI 32% and in definitely ruled out AMI 23% (p < 0.001). When simultaneously considering age, sex, previous history of cardiovascular disease and smoking, the development of AMI appeared as an independent predictor of death (p < 0.001). Thus, among patients hospitalized due to suspected AMI, 10-year mortality after discharge from hospital was directly related to the diagnosis during the first 3 days in hospital.