The authors report a successful hepatolobectomy of Caroli's disease (segmentally dilatated intrahepatic bile ducts). They also give a survey of congenital and acquired bile duct dilatations, with a view to differential diagnosis and medical treatment. When Caroli's disease is suspected, echography and ERCP can be a valuable diagnostic aid. The definitive cure i. e. the elimination of the anatomical basis of recidive cholangitis, can only be achieved by the resection of the liver containing the dilated intrahepatic bile ducts. Postoperative administration of antibiotics and anticholelithic drugs can help the liver to full recovery.