Glucose oxidation and thermogenesis were studied after a peritoneal (P) and an oral (O) glucose load in nine chronically uremic patients undergoing continuous ambulatory peritoneal dialysis (CAPD) for 24.4 +/- 5.8 months. The O load (50 g) given was equivalent to the amount of glucose absorbed over six hours through the peritoneum of the subjects (51.7 +/- 3.3 g). Glucose oxidation and energy expenditure were obtained using indirect calorimetry in basal state and over the six hours following the glucose load. Glucose oxidation rate was higher from 60 to 180 minutes after O than after P (P < 0.05), with peak values of 3.85 +/- 0.28 mg.kg-1.min-1 and 2.80 +/- 0.17 mg.kg-1.min-1 respectively (P < 0.05). Cumulated glucose oxidation over six hours was 53.6 +/- 0.6 versus 47.0 +/- 3.4 g after O and P respectively (NS). Glucose-induced thermogenesis was 8.7 +/- 2.9% versus 5 +/- 1.9% after O and P, respectively (NS). The route of administration of glucose induces different kinetics of the glucose oxidation rate, but a similar amount of glucose absorbed either by the peritoneum or by the gut contributes in a similar extent to glucose and energy balance.