Caroli's disease is characterized by multifocal segmental dilatation of the intrahepatic bile ducts. It is a rare congenital condition, which appears to be autosomal recessively inherited in most cases. There are two forms of disease, one associated with congenital hepatic fibrosis and a simple form occurring alone. Recent reports suggest that the simple form may be as common as that with congenital hepatic fibrosis. Other conditions, including choledochal cyst and renal cystic disease, are frequently associated. The major clinical feature is recurrent cholangitis, which may be complicated by intrahepatic calculi and hepatic abscess formation. There is good evidence that malignancy complicates Caroli's disease in approximately 7% of cases. The diagnosis rests on demonstrating that the cystic liver lesions are in continuity with the biliary tree. Modern imaging techniques allow the diagnosis to be made more easily and without invasive imaging of the biliary tree. The treatment depends on the clinical features and the location of the biliary abnormality. When the disease is localized to one hepatic lobe, hepatectomy relieves symptoms and appears to remove the risk of malignancy. In diffuse Caroli's disease, treatment options include.