Eighteen patients with advanced renal cancer were treated with 0.15 mg/kg/day floxuridine by continuous intravenous infusion for 14 days with 3 million IU/m²/day alpha interferon subcutaneously three times weekly. Treatment cycles were repeated every 28 days. Floxuridine dosages were escalated to a maximum of 0.2 mg/kg/ day and alpha interferon dosages were escalated to a maximum of 6 million IU/ m²/day depending on patient tolerability. A total of 49 treatment courses were administered with a median of 2.7 courses per patient. Of 14 assessable patients, there were no complete or partial responses. Eight patients (57%) had stabilization of disease. The median survival for patients with stable disease was 20.9 months and for all 18 patients was 7.2 months. Grades 3 and 4 toxicities included diarrhea (44%), nausea/vomiting (28%), mucositis (11%), fever (22%), and fatigue (50%). Dose-limiting toxicities were primarily gastrointestinal symptoms. There were no treatment-related deaths. This combination in the dose schedule used did not result in any significant objective tumor response but was associated with considerable toxicity.