Ninety-one patients with metastatic colorectal cancer were treated with continuous ambulatory 5-fluorouracil(5FU) infusion 250-300 mg/m2/day through a chronic indwelling central venous catheter. Twenty-six of the 91 patients (29%) had received previous bolus 5FU. Fifty-eight of the 91 patients (64%) had two or more sites of disease, and 74 of 91 patients (81%) had liver metastases. Results were complete remission in 5 of 91 (6%), partial remission in 25 of 91 (27%), stable disease in 33 of 91 (36%), and progressive disease in 28 of 91 (31%), for an overall response rate of 30 of 91 (33%); median duration of response was 7 months. Twenty-six of 65 previously untreated patients (40%) experienced objective response. Median survival from initiation of treatment for all patients was 11 months. Forty-one percent of patients experienced no significant toxicity and were able to continue therapy without treatment interruption. Toxicities necessitating treatment interruption included stomatitis in 35 patients (39%), hand-foot syndrome in 33 patients (36%), and diarrhea in 10 patients (1 1 %). No significant myelosuppression or serious catheterrelated complications were encountered. We conclude that continuous systemic venous infusion of 5FU produces a higher response rate than traditional bolus 5FU schedules, with apparent enhancement of survival and easily managed toxicity.