To evaluate the effects of medically supervised exercise in subjects with recent myocardial infarction, 42 patients have participated in three months or more of a gym program of walk-jog sequence, calisthenics, and volleyball. There was a significant (P<.01) increase in mean value for submaximal treadmill exercise test (STET) time (or exercise capacity). The exercise quotient decreased in all but one patient (P<.01), and mean value for resting and peak exercise systolic blood pressure and resting heart rate, body weight, and serum triglyceride level, also decreased substantially. Of three patients with abnormal changes for ischemic heart disease on initial STET, two had a normal STET on retesting. No deaths occurred in this group of patients. The data suggest that a medically supervised gym exercise program for patients with recent myocardial infarction is feasible, safe, and beneficial.