Primary sclerosing cholangitis (PSC) is a disease characterized by obliterative inflammatory fibrosis usually affecting both the intrahepatic and extrahepatic portions of the biliary tree. Cholangiography is the accepted method for making the diagnosis. Histologic findings can be highly suggestive of PSC, particularly when concentric periductal fibrosis is present (one third of patients), but the findings are usually nondiagnostic [1]. The cholangiographic appearance of PSC includes a broad spectrum of features [2]. On the basis of a study of these features in 40 patients with PSC, we classified the abnormalities into three types of intrahepatic and four types of extrahepatic abnormalities depending on the extent of bile duct narrowing, the severity of narrowing, contour abnormalities, and prestenotic dilatation. In this article, we present a modified classification and discuss the clinical implications of each class.