The mortality and morbidity of 150 young (less than 45 years) survivors of myocardial infarction was studied prospectively over a 10-year period. Thirty-seven deaths (36 due to coronary artery disease) occurred from one month to 10 years after myocardial infarction and the cumulative 10-year mortality was 27 per cent compared with 5 per cent in the general population. High initial lactate dehydrogenase levels and continued cigarette smoking after infarction were associated with a poor long-term survival. Angina was present at some time during follow-up in 60 per cent of patients. Severe limitation of exercise tolerance was present in 18 per cent, and 16 per cent had radiological evidence of cardiomegaly. Left ventricular failure occurred in 13 patients and carried a very poor prognosis. Unemployment in 95 men who survived 10 years was 32 per cent, half of whom had never returned to work following infarction, compared with a regional value of 7 per cent. We have shown that there is a prolonged and persistent mortality and morbidity in young survivors of myocardial infarction with a high level of male unemployment. Careful rehabilitation should reduce the economic loss to the community together with persuasive advice against cigarette smoking.