Primary sclerosing cholangitis (PSC) is an important liver disease with major morbidity and mortality. The diagnosis of PSC is confirmed by magnetic resonance cholangiopancreaticography, and endoscopic retrograde cholangiopancreaticography is performed in patients needing therapeutic endoscopy. As a result of the unknown cause of the disease, current medical therapies are unsatisfactory. Nevertheless, high-dose ursodeoxycholic acid should be recommended for treatment of PSC patients because there is a trend toward increased survival. Dominant bile duct stenoses should be treated endoscopically. However, liver transplantation continues to be the only therapeutic option for patients with advanced disease. Estimation of prognosis and timing of liver transplantation should be determined individually for each PSC patient on the basis of all results. The diagnosis and treatment of cholangiocarcinoma (CC) still remain a challenge in PSC patients. Early diagnosis of CC certainly is a prerequisite for successful treatment with surgical resection or innovative strategies such as neoadjuvant radiochemotherapy with subsequent orthotopic liver transplantation. Therefore, endoscopic techniques such as cholangioscopy and/or intraductal ultrasound may be useful diagnostic tools in patients with stenoses suspicious for malignancy. Liver Transpl 14:735–746, 2008. © 2008.