The risk for developing acute liver failure after halothane exposition was calculated between 1:8,000 and 1:36,000. The case report given on a 22 year old man with halothane-induced hepatic failure is unusual, because the typical risk factors as age over 40, female sex, obesity, and previous exposure to halothane were not present. Two days after exposure to halothane the patient suffered acute liver failure with severe coagulopathy (factor V = 5% activity), and encephalopathy grade IV complicated by renal failure and respiratory insufficiency. Maximal increases of enzymes in blood were AST 3900 U/L, ALT 2570 U/L, LDH 10600 U/L. After six days the patient underwent liver transplantation with complete anuria and instable circulation. Explanted liver showed massive necrosis (70% of parenchyma) and fatty changes. The liver transplant had immediately a good function and renal failure resolved within three days. In the follow-up of 3 1/2 years the patient suffered no further complications. Culturing the patient's lymphocytes in the lymphocyte transformation test a strong reaction could be detected with a stimulatory index of 20. Maximal proliferation was observed when lymphocytes were incubated with plasma metabolites of a volunteer drawn 120 minutes after anesthesia with halothane was started.