The authors treated 42 metastatic renal cell carcinoma (RCC) patients who had received no previous chemotherapy or radiation therapy with circadian venous continuous infusion of 5-fluoro-2-deoxyuridine (FUDR). The drug was delivered by Medtronic Synchromed implantable pump (Medtronic, Inc., Minneapolis, MN) in 14-day cycles alternating with 14-day intervals of heparinized physiologic saline infusion. In the course of 24 months 444 cycles of therapy have been given for a total of 12449 days of pump function. Of the patients observed for at least 3 months (range, 3 to 23 months; median, 7 months) three showed complete response (7%; 95% confidence interval, 0% to 15%), three partial response (7%; confidence interval, 0% to 15%), 18 stable disease, and 18 showed progression. Eighteen patients, all with advanced disease at the time of implantation, were living 6 months after treatment started. Circadian continuous central venous infusion of FUDR is minimally toxic. The FUDR can be delivered safely and conveniently in this way for long spans. This therapy is as active as any currently available treatment, is administered in an entirely outpatient setting, and is associated with a normal quality of life.