To assess the potential benefits of perioperative glucose administration, the plasma concentrations of insulin, free fatty acids, ketone bodies, amino acids, lactate, and pyruvate were measured in 20 patients undergoing partial gastrectomy Ten patients received intravenous glucose at 10 g/h during the operation, and the other 10 patients, as control, received no glucose. Plasma glucose, insulin activity, pyruvate and alanine concentrations in the glucose-receiving group increased significantly during the operation in comparison with the control group. In contrast, in the glucose-receiving group the plasma ketone bodies and branched-chain amino acids, especially leucine and isoleucine, decreased significantly during surgery. These results suggest that administration of glucose stimulated insulin secretion and resulted in accumulation of the substrates such as pyruvate and alanine which were utilized readily in the body. Glucose administration is useful in suppressing catabolism during upper abdominal surgery.