5-Fluorodeoxyuridine (FUDR) was infused continuously into the hepatic artery for 14 days a month at an initial dose of 0.3 mg/kg per day in 45 patients with liver metastases from colorectal carcinoma. In 41 adequately treated patients, partial responses (greater than 50% tumor regression) were observed in 12 (52%) of 23 previously untreated patients, and three (17%) of 18 previously treated patients. Severe gastrointestinal toxicity was endoscopically documented in 19 (46%) patients; 12 (29%) had discrete ulcers, and seven had diffuse gastritis or duodenitis. Significant hepatic-enzyme abnormality was seen in 29 patients (71%) and an elevated serum bilirubin in nine (22%). A significant factor influencing survival was the extent of tumor involvement in the liver; patients with less than 20% involvement have not yet reached a median survival at 13 months versus six months for patients with greater than 60% involvement (p less than 0.001). Studies comparing regional to systemic chemotherapy and stratifying patients according to the extent of hepatic tumor burden are needed to assess the true impact of hepatic infusion on response and survival.