Caroli's disease is a liver disease with segmental cystic dilatation of the intrahepatic bile ducts. It belongs to the group of congenital ductal plate malformations. With an incidence of only 0.05% of all liver cases in the Liver Registry of the University of Cologne, it is a very rare disorder. Caroli's disease is usually combined with cholangitis and bile duct stones. Control of these infections and maintenance of biliary drainage are the main therapeutic aims. The development of intra epithelial neoplasia and invasive carcinoma are rare complications. We report a case of Caroli's disease with the development of cholangiocarcinoma and review the literature.