AbstractExercise capacity is documented to be poor in patients with end stage renal failure undergoing regular hemodialysis, but there is little information about exercise capacity in patients on continuous ambulatory peritoneal dialysis (CAPD). We studied a group of 18 patients undergoing CAPD, with a variety of cardiorespiratory disorders, using a progressive load treadmill exercise test. The influence of intraperitoneal fluid on work capacity was also assessed. The mean maximum oxygen uptake (VO2max) of the CAPD patients was reduced considerably (14.6 ml kg‐1min‐1) compared with matched control subjects (33.6 ml kg‐1min‐1). This corresponded to the difficulty experienced by these patients in carrying out daily activities. There was no significant change in VO2max or in maximum heart rate with the peritoneal cavity full. We conclude that physical fitness is poor in CAPD patients and that the infusion of dialysis fluid into the peritoneal cavity does not affect physical work capacity