Toxicities and complications were prospectively analyzed in patients with liver metastases receiving hepatic intra-arterial (IA) and systemic intravenous (IV) floxuridine (FUDR) with the Infusaid (Intermedics-Infusaid Corp., Norwood, MA) implantable pump. Among 55 patients treated with IA FUDR (0.3-0.1 mg/kg/day X 14, every 28 days), elevations in liver enzyme values, not attributable to disease progression, developed in 96% of patients. Serious biliary toxicity occurred in 31 patients (56%). In 16, biliary sclerosis was documented radiographically and was diagnosed clinically in 15 additional patients. Ten patients were hospitalized for biliary toxicity, including five who required cholecystectomy for acalculous cholecystitis. Because of the high reported incidence of serious gastroduodenal toxicity after IA FUDR infusion, our procedure for hepatic arterial cannulation was designed to eliminate misperfusion of the stomach and duodenum with drug; none of our patients experienced FUDR-associated gastroduodenal ulceration or bleeding. Cyclic IV FUDR (0.05-0.15 mg/kg/day X 14, every 28 days) was administered to 31 participants of the Northern California Oncology Group trial (3L-82-1) of IV versus IA FUDR. Dose-limiting toxicity was diarrhea. Serious toxicities were: protracted diarrhea (three), dermatitis (two), tear duct stenosis (two), and stomatitis (two). Three patients were hospitalized for toxicity. No hematologic or biliary toxicity occurred. The optimal route for treatment of hepatic metastases with continuous FUDR infusion has not yet been established. Systemic IV infusion has low morbidity, but preliminary response data need to be substantiated in controlled clinical trials before there can be widespread clinical application. High response rates for IA infusion have been previously documented. Morbidity due to acalculous cholecystitis and gastroduodenal ulceration can now be avoided. Despite significant progress in characterization of hepatobiliary toxicity, it remains dose-limiting. Continuous IA FUDR infusion should remain under the aegis of dedicated treatment centers until standardized protocols with diminished toxicity are established.