In two 19-year-old girls with Wilson's disease the condition took a fulminant course, including a poor general state, marked haemolysis and ascites. In the first patient the diagnosis was histologically confirmed only after three weeks, and onset of treatment with penicillamine was therefore delayed. With this medication the concentrations of alkaline phosphatase, cholinesterase and total bilirubin returned to normal, but again became abnormal after about seven weeks. Despite substitution of clotting factors thromboplastin time remained reduced. She died 82 days after the onset of symptoms. In the second patient, treatment with penicillamine was started at once, without waiting for histological confirmation. All laboratory values became normal and remained so. It is concluded from these observations that liver transplantation is indicated if the abnormal values for cholinesterase, thromboplastin time and bilirubin do not remain normal after six weeks and if the initial suppression of alkaline phosphatase continues or occurs again.