This study prospectively evaluates the long-term prognosis of patients admitted with chest pain under suspicion of acute myocardial infarction (AMI) with and without confirmed diagnosis. All patients below 76 years of age, free of other severe diseases and alive at discharge, who were admitted to a coronary care unit of a well-defined region during 1 year, constituted the study population. In all, 275 patients with and 257 patients without confirmed AMI (non-AMI) were included. During 7 years of follow-up, 122 cardiac events (96 cardiac deaths and 26 nonfatal AMI) occurred in the AMI patients, and 69 (44 cardiac deaths and 25 nonfatal AMI) were observed in the non-AMI patients. Using univariate analysis, the following risk variables were significantly related to an impaired prognosis of non-AMI patients: age, a history of previous AMI, angina pectoris, clinical heart failure, diabetes and ST or T changes in the electrocardiogram (ECG) on admission. By multivariate analysis, the following risk factors contained independent prognostic information for non-AMI patients: (1) a history of angina pectoris and (2) ST and T changes on the ECG on admission. We conclude that a subset of non-AMI patients at high risk for cardiac events even in the long term can be identified from the medical history and the ECG on admission. These patients should be carefully evaluated prior to discharge, whereas patients without signs of ischemic heart disease have an excellent prognosis.