Caroli's disease is characterized by dilatation of the intrahepatic bile ducts. Cholangitis, liver cirrhosis and development of a cholangiocarcinoma are possible complications. For optimal therapy, a correct diagnosis of the extent of the disease is mandatory. The present report demonstrates that the combination of endoscopic retrograde cholangiography and ultrasound may lead to a more reliable diagnosis of the extent of Caroli's disease. It is therefore essential to perform ultrasound in all these patients.