The effect of a dialysate exchange with both 1.5 and 4.25% glucose solutions on plasma levels of glucose, insulin, gastric inhibitory polypeptide (GIP), and glucagon has been investigated in 5 continuous ambulatory peritoneal dialysis (CAPD) patients. Only in the case of the 4.25% solution did plasma glucose levels rise above 100 mg/dl. 4 of the 5 patients responded to this change with a marked insulin secretion. Employing the 1.5% solution, plasma glucose remained stable and only a slight insulin stimulation was observed in 2 patients. It is concluded that provided the 4.25% dialysates are used only occasionally, there will be no continuous stimulation of the pancreatic β-cells due to absorption of glucose from the dialysate alone during CAPD treatment. GIP levels are highly elevated in CAPD patients. A dialysate exchange with either a 1.5 or a 4.25% glucose solution had no effect on this gastrointestinal hormone. Hyperglucagonemia was also observed in this collective. An initial suppression of glucagon levels occurred in 4 of the patients after a 4.25% dialysate exchange. The 5th patient demonstrated an initial rise followed by a later decrease in glucagon, a response similar to that reported in adult onset diabetes after an oral glucose tolerance test.