The metabolic profiles of 14 patients with prolonged abdominal sepsis were analysed on the second day after laparotomy. The profiles of survivors were compared with those of non-survivors who died one to five days after the time of evaluation due to uncontrollable multiple organ failure. In the non-surviving patients plasma glucose and glucagon levels were significantly higher than in surviving patients. The plasma concentrations of phosphoserine, cysteine, valine, phenylalanine, and 3-methylhistidine were found to be significantly increased in non-survivors and their muscle tissue showed significantly decreased concentrations of glutamine, proline and lysine with increases in valine and leucine. A correct classification of non-survivors and survivors could be obtained from the plasma and muscle amino acid concentrations, the highest discriminant power being from muscle glutamine. In severe sepsis metabolic changes correlate with the outcome of the patients, and amino acid metabolism seems to be characterised by low concentrations of muscle glutamine and high levels of the branched chain amino acids possibly indicating an inhibited intracellular glutamine formation in muscle tissue.