The authors developed a dog model for the biliary sclerosis that occurs as a severe complication of protracted hepatic arterial floxuridine (FUDR) infusions (using implanted drug delivery systems) in patients with hepatic cancers. Infusaid pumps attached to hepatic arterial catheters were used for protracted infusions in ten mixed breed hounds. To allow repeated cholangiograms, the animals' gallbladders were removed and catheters connected to subcutaneous infusion ports were positioned in the cystic ducts. Five treated dogs received FUDR 0.3 mg/kg/day through the pump for a total of 30 days. Five control dogs received only saline through the pump. Cholangiograms were obtained before and after treatment in all animals. In the control group, serum liver function test results and the cholangiographic appearance of the biliary tree remained within normal limits. By contrast, in the FUDR-treated group, serum glutamic-pyruvic transaminase and alkaline phosphatase progressively rose above normal, starting 2-3 weeks into FUDR infusion, followed by hyperbilirubinemia (7-28 mg/dl peak levels) beginning 4 to 6 weeks after initiation of the drug infusion. Cholangiograms revealed focal strictures involving the central bile ducts (five dogs) and diffuse attenuation of the intrahepatic ducts (four dogs). Thus, the liver function abnormalities and the cholangiographic findings in this dog model mimic the hepatobiliary toxicity in sensitive patients receiving similar treatment.