Three hundred and ten patients, 129 under sixty-five years (group A) and 181 over this age (group B), were studied to determine the clinical differences between young and elderly patients with acute myocardial infarction. Women were significantly more present in group A and heavy smokers in group B. Hypertension, although not significantly, was more frequent among the elderly. Serial ECG and enzyme determinations followed the same classic pattern in both groups. Age did not influence neither the localization of the infarction nor the incidence of subendocardial infarction. Young patients remained more often in functional class I, whereas class IV was twofold more frequent among the older. First and second degree A-V block were equally present in the two groups, while third degree A-V block was significantly more frequent in patients over 65. Finally, as expected, in-hospital mortality was significantly higher (34% vs 16% p less than 0.001) among the older patients.