To assess the psychological effects of exercise training in hemodialysis patients, 4 dialysis patients, matched by age, sex and medical history with 4 controls, received psychological testing before and after a 6-mo. period of exercise training. The trained patients had a 28% improvement in graded exercise treadmill stress test duration and a 13% improvement in aerobic capacity. This was associated with a significant reduction in anxiety and depression (P < 0.06), but no measurable change in these moods occurred in the control groups. Exercise training may improve psychological functioning in dialysis patients.