Data on the long-term prognosis of acute myocardial infarction (AMI) in young patients are limited. This study investigated long-term survival and risk predictors in a series of 108 consecutive patients ≤40 years old who represented 4% of 2,644 patients who presented with AMI at a single center between June 1986 and April 1992. Four patients died soon after admission. The overall mortality rate of the 104 survivors was 25.5% at 15 years. The mortality rate was higher in patients who had type 1 diabetes mellitus (p = 0.01), long-term excessive alcohol intake (p = 0.035), peripheral arterial disease (p = 0.004), previous AMI (p = 0.04), anterior AMI (p = 0.01), and depressed left ventricular ejection fraction (p <0.0001). Cumulative survival rates (Kaplan-Meier analysis) at 1, 5, 10, and 15 years were 99%, 95%, 86%, and 75%, respectively. Event-free survival rates (death, AMI, coronary intervention, severe angina pectoris, malignant arrhythmias, and congestive heart failure) at the same times were 88%, 76%, 60%, and 43%, respectively. The strongest independent predictors of the long-term mortality rate were ejection fraction ≤45% (odds ratio 4.4, 95% confidence interval 1.6 to 12.4, p <0.001) and peripheral arterial disease (odds ratio 45.9, 95% confidence interval 3.79 to 555, p <0.0001). These data suggest that the long-term prognosis and functional status of young patients who have AMI are not benign, especially when ejection fraction is decreased or peripheral atherosclerotic disease is present.