The effect of citrate on sodium, potassium chloride, and water absorption in the presence of glucose from the whole rat small intestine was studied by an in vivo marker perfusion technique. The perfusion solutions contained glucose and were similar in their electrolyte composition to the currently recommended oral rehydration solution for the treatment and prevention of diarrheal dehydration. Significantly more sodium and water absorption occurred from the citrate-containing solution than from the one without citrate. It is concluded that citrate enhances net sodium absorption from a glucose electrolyte solution in the rat small intestine independent of glucose-stimulated absorption.