Primary sclerosing cholangitis (PSC) can lead to the development of cholangiocarcinoma (CCA). The tumor may present as an intrahepatic focal cholangiocellular carcinoma but more often as a ductal infiltrating desmoplastic lesion. CCA is found synchronously with the diagnosis of PSC in 20-30% and within 1 year in 50%. During later follow-up, the yearly developmental rate of CCA is 0.5-1.5%. Most patients with PSC and CCA do not yet have cirrhosis but present with a severe stenosis at the hilum of the liver. This type of tumor is difficult to diagnose by imaging techniques.(18)F-FDG-PET scanning and CEA or CA 19-9 are not early diagnostic tools. Regular MRI, multislice CT, and repeated endoscopically obtained brush cytology of stenotic lesions are recommended. The recent use of more extensive surgical resection techniques in patients with CCA results in 5-year survival rates of > or =50%. If tumors are small or incidental findings, liver transplantation leads to a 3- to 5-year survival rate of 35%. Pretransplant radiotherapy with 5-FU chemosensitization followed by endoscopic brachytherapy with iridium-192 seems to greatly improve the outcome of transplantation. Treatment with ursodeoxycholic acid may prevent development of CCA.