Primary sclerosing cholangitis (PSC) is a chronic inflammatory condition of the bile ducts of unknown etiology. It is characterized by diffuse inflammation and stricturing of the entire biliary tree, eventually resulting in cirrhosis of the liver. Patients with PSC are at increased risk for the development of cholangiocarcinoma (CCA), a cancer arising from bile duct epithelium. This risk is estimated to be approximately 1 to 1.5% per year. It is postulated that chronic inflammatory changes in the biliary epithelium promote CCA formation. The prognosis of CCA is fatal. The only potentially curative therapy is surgical; however, only a minority of patients qualify for surgical treatment.