In the third week after acute, definitive myocardial infarction in 45 patients (34 males, 11 females) at an average age of 63 years a submaximal and symptom-limited, respectively, exercise test was performed. With 57 watt and a watt pulse of 0.53 the males reached significantly higher performances than the females. 17 patients who had to finish the test above all on account of the transition of the submaximal heart rate showed a high performance of more than 50 watt. On the other hand, patients showed low performances who in the acute phase had transient, medicamentously controllable bradytachycardias, right cardiac insufficiency or depression of the blood pressure or finished the test on account of the depression and the elevation, respectively, of the ST segment. In the first year died 5 patients who all were older than 70 years and had shown low performances between 25 and 50 watt in the exercise test of the third week, connected with depressions of the ST segment of higher degree.