In 171 patients a submaximal exercise test was performed 3-6 weeks after the first acute myocardial infarction. No complications in connection with exercise test were observed. The incidence of ST/T-segment changes was significantly higher in patients over age 50. Patients over age 60 have a significantly higher incidence of PVCs as well as complex ventricular arrhythmias. In this patient group the incidence of ventricular arrhythmias was higher in patients with ST/T-segment changes during exercise. In the younger patients there was no correlation between incidence of ST/T-segment changes and arrhythmias. A high percentage of patients with no arrhythmias during exercise also had no arrhythmias during Holter. During follow up the average mortality rate was 3.6% and was not significantly different in the four age groups.