Intestinal glucose and water absorption in response to glucose has been studied in tropical enteropathy with a view to determine the optimum glucose concentration in oral rehydration solutions for use in the tropics. Maximum jejunal water and sodium absorption occurred from an 80-mM glucose-sodium chloride solution (-285.7 +/- 46.0 ml/30 cm/h and -31.8 +/- 3.8 mM/30 cm/h, respectively) during in vivo steady-state jejunal perfusion. At perfusate glucose concentrations greater than 250 mM, however, jejunal water and sodium secretion occurred. In the ileum, maximum glucose-stimulated water absorption (-91.1 +/- 27.1 ml/30 cm/h) was significantly less than in the jejunum. Glucose absorption demonstrated saturation kinetics in both the jejunum and ileum. The half-saturation concentration was higher in the jejunum (167 mM) compared to the ileum (28 mM). This study suggests that the optimal glucose concentration for oral rehydration solutions used in the tropics should be 80 mM, as lower and higher concentrations result in diminished jejunal water absorption.