During a 2-year period, cholangiography was performed on 17 patients with clinical evidence of cholestasis who were receiving hepatic intraarterial floxuridine (IA-FUDR) infusions for treatment of metastatic colorectal adenocarcinoma. The development of cholestasis was associated with persistently elevated alkaline phosphatase, but serial CT examinations of the liver showed no progression of the tumor. All patients had cholangiographic abnormalities (by endoscopic retrograde cholangiopancreatography, percutaneous transhepatic cholangiography, or operative cholangiography) of the biliary ductal system similar to those in idiopathic sclerosing cholangitis. Certain features, however, appear specific to IA-FUDR-induced cholestasis. All patients studied had segmental involvement at the common hepatic duct bifurcation. The cystic duct and gallbladder were often involved, but the distal common bile duct was spared. Histologic features of periportal and periductal fibrosis were present in specimens obtained from percutaneous liver biopsy in three patients, cholecystectomy in four patients, and autopsy in two patients. When clinical signs of hepatic dysfunction occur in the absence of tumor progression, biliary sclerosis must be suspected.