Physical training causes an increase of aerobic capacity in normal and cardiac patients. The influences of training plus placebo and training plus verapamil have been studied in a double-blind randomized trial on 40 patients recovering from acute myocardial infarction. The two groups were comparable as to clinical characteristics, initial work capacity, and amount of stress tolerated during the training sessions.The training produced a significant increase of total work capacity and maximum VO<sub>2</sub>, in both groups; the difference between the means of the two groups was not significant. The variation of heart rate, rate pressure product at different work loads and cardiac volume after training were significantly lower in the verapamil group. The anginal threshold did not change in the placebo group and showed a trend to increase in patients treated with verapamil. These results suggest that carefully observed rehabilitation markedly improves the physical capacity of the patients after acute myocardial infarction. Such improvement is enhanced by treatment with verapamil.