The aim of the investigation was to determine the changes in intermediary metabolism that occur in cases of ileus, and to develop a concept for parenteral perioperative nutrition on a pathophysiological basis. Seventeen metabolically healthy patients, suffering from mechanical ileus, have been evaluated. Besides the nonspecific metabolic changes characteristic of the postaggressive metabolism (abnormalities in peripheral glucose utilization, gluconeogenesis, lipolysis, proteolysis) we were able to demonstrate elevated serum levels of albumin, lactate and arachidonic acid preoperatively in these patients. The plasma histamine levels lay within normal limits. In the immediate postoperative phase (i.e. from 1.-3. postoperative day) we found a marked reduction in the serum levels of glucoplastic amino acids (about 30%), albumin (40%), pre-albumin (80%) and cholesterol (50%). We therefore suggest that, apart from electrolyte solutions, patients with an ileus should receive fructose (1600 kcal/day) preoperatively and from the first postoperative day amino acids (1 g/kg of body weight) and human albumin (as required) should be administered in addition.