Institutionalized severely and profoundly mentally retarded adults participated in two exercise programs. One group of 19 subjects performed a circuit-training regimen consisting of treadmill walking, stationary bicycle riding, rowing, and calisthenics. Exercise sessions lasted 60 minutes and were performed every third day during an 18-week training period. A second group of 19 subjects participated in an 18-week jogging regimen which consisted of running distances of 1/2, 1, or 1 1/2 miles each session. The exercise requirements in both programs were increased progressively during the course of training. Subjects adapted quickly to both exercise regimens and almost all improved their physical endurance and ability to exercise. It is suggested that the highly motivating characteristics of exercise may provide educators with a training medium through which new skills can be taught to severely and profoundly mentally retarded adults.