A report is given on 2 patients with postoperative liver and kidney insufficiency who showed a hereditary fructose intolerance (HFI) after the infusion of fructose and sorbitol. The pathophysiological and clinical signs of this rare disease are described. Since irreversible organ damage occurs already after the infusion of more than 30 to 40 grams fructose or sorbitol, every therapy is questionable. Therefore, prophylactic measures are important in infusion therapy. Particularly in emergency patients and during the preanaesthetic investigation of patients, HFI must be taken into account in adults.