We compared the angiographic findings, coronary risk factors and five years prognosis in 200 patients < or =45, and 260 patients >45 years old who where admitted with an acute myocardial infarction. We found that family history and smoking were the most common risk factors in patients < or =45 years old P<0.04, P<0.0001, respectively, and hypertension and diabetes mellitus were more prevalent in patients >45 years, P<0.00001 for both. Young patients had a higher incidence of normal coronary arteries and a lesser one of triple vessel disease in comparison with old ones P<0.001 and P<0.04, respectively. There was also a tendency for young patients to have a higher frequency of single vessel disease. The long-term prognosis was favourable in the younger age group since the survival rate was much better, as well as the quality of life. Death in the young patients seems to be very often electrical owing to sudden ventricular fibrillation, whereas death in the elderly is more often associated with congestive heart failure.