The effects of continuous ambulatory peritoneal dialysis (CAPD) on glucose tolerance and serum immunoreactive insulin and glucagon responses to oral glucose over the first year of therapy were studied in 13 uremic patients. Oral glucose tolerance tests were performed before treatment started, and again after 3 and 12 months on CAPD. Before CAPD, the patients showed decreased glucose tolerance. However, neither fasting blood glucose and serum insulin and glucagon levels nor the insulin and glucagon levels during the tests were significantly different from results obtained in 13 healthy controls. During CAPD, the mean intraperitoneal supply of glucose from the dialysates varied between 121 and 245 g/day and did not change during the study period. Glucose tolerance and hormone responses to glucose did not change during the study period. No patient developed manifest diabetes mellitus. We conclude that glucose intolerance in uremia persists during CAPD, but despite the continuous peritoneal absorption of 100-200 g of glucose during CAPD, the treatment had no effect on glucose tolerance and insulin secretory response.