This study examines the effects of 12 months of endurance exercise training (cycling, walking and jogging) on lipid profiles, glucose metabolism, blood pressure, anemia and psychological function in 14 hemodialysis patients. Maximal aerobic capacity (VO2max) increased 18% in the exercisers (p less than 0.01), but did not change in 11 controls. This was associated with a reduction in depression, a decrease in dosages of antihypertensive medications, a significant increase in hematocrit and hemoglobin levels (red cell mass rose, plasma volume did not change), a decrease in plasma triglyceride by 23% (p less than 0.05) and an increase in high-density lipoprotein cholesterol (HDL-C) levels by 21% (p less than 0.01) (both HDL-C and triglyceride levels worsened in the sedentary controls), and an 18% increase in glucose disappearance rates (p less than 0.05) in spite of a 52% decrease in fasting insulin levels (p less than 0.01), suggesting that insulin sensitivity improved. These results demonstrate that some of the complications present in hemodialysis patients may be caused by their sedentary life-style, rather than endstage renal disease itself. This suggests that rehabilitation through exercise is possible for these patients. By reducing coronary risk factors in hemodialysis patients, exercise training may also decrease their heightened morbidity and mortality from atherosclerotic complications. These possibilities need to be examined in a longitudinal study.