Primary sclerosing cholangitis (PSC) is a chronic progressive liver disorder that is characterized by ongoing inflammation,obliteration, and fibrosis of both intrahepatic and extrahepatic bile ducts. Diffuse strictures with short intervening segments of normal or dilated bile ducts produce the characteristic beaded appearance on cholangiography.The pathogenesis of PSC is unknown, but available data suggest that both immunological and nonimmunological host defenses may be impaired (1). Hence, the normal intestinal flora or their metabolic products may play a pathogenic role (1). The disease is usually progressive and may lead to cirrhosis and portal hypertension. PSC is an uncommon disorder for which there are few extensive prevalence data. The estimated prevalence of PSC in the United States,based on studies of inflammatory bowel disease, is 6.3/100,000 (2). A true population-based study has only been done in Norway, where incidence and point prevalence were 1.3 and 8.5 per 100,000 inhabitants, respectively. This compares to incidence and point prevalence of 1.6 and 14.6 for primary biliary cirrhosis. These values seem to be higher than in the rest of Europe or the United States. The recognition of PSC as a distinct liver disease is relatively recent.Until 1970, fewer than 100 patients with PSC had been reported. However, the introduction of endoscopic retrograde cholangiography has changed our perception of this disease. It is now recognized more frequently and is the fourth leading indication for liver transplantation in adults(3). Here we will review the clinical features of PSC, and then propose recommendations regarding appropriate diagnostic and therapeutic strategies. There is no proven medical treatment short of liver transplantation. However, there is effective treatment of many of the symptoms associated with PSC.