Nine patients receiving maintenance high-efficiency hemodialysis were studied before and after a 12-week conditioning program to determine the efficacy of exercise immediately following hemodialysis. Each patient performed a combination of bicycle ergometry on the Schwinn Air-Dyne ergometer (SAE) and treadmill walking three times a week for a total exercise time of 15–35 min per session. A low-level Bruce treadmill test and an exercise test on the SAE were administered before and after training. Hematological, serum electrolyte, and serum lipid profiles were also determined before and after training. Following training, there were improvements in exercise capacities for both treadmill walking and ergometry on the SAE. Although a significant increase in serum apolipo-protein Al was seen following exercise, no significant changes were observed for total cholesterol, low-density -lipoprotein cholesterol, high-density-lipoprotein cholesterol or apolipoprotein B. Additionally, no significant changes were seen in hematological parameters and serum electrolyte profiles following the exercise program. The 9 patients demonstrated an average compliance record of 74%. This study demonstrated that patients on high-efficiency hemodialysis can safely engage in an exercise program immediately following dialysis at intensities and frequencies that can improve their physical work capacitie