Acute effects of a low-dose bradykinin infusion (30 ng/kg per min) on carbohydrate metabolism were studied in five patients after major burn injury. Peripheral glucose uptake was not affected but glucose oxidation and alanine flux were increased by 15% and 10%, respectively. These findings are compatible with an increase in glycolytic flux by an action of bradykinin. Nineteen patients who had undergone major gastro-intestinal surgery were studied in a randomised trial of chronic (6 day) bradykinin administration. Patients in the bradykinin group had a significantly improved rate of nitrogen retention (cumulative N balance, -0.014 [SE 0.064] vs -0.175 [0.048] g N/kg) in controls and significantly better nutritional indices. Manipulation of metabolism in surgical patients by bradykinin may have beneficial effects on nitrogen and protein dynamics, possibly mediated by improved aerobic and anaerobic glycolysis.