Fluoropyrimidines are known to have modest activity in the treatment of metastatic renal cell carcinoma (RCC). Capecitabine is an orally administered prodrug that is converted to fluorouracil and is of potential use in the treatment of this disease. We conducted a Phase II clinical trial of capecitabine administered as a single agent to patients with metastatic RCC. The treatment consisted of 1250 mg/m(2) capecitabine orally, twice daily (2500 mg/m(2) per day) days 1-14, repeated every 21 days. There were 15 patients, including 13 men and 2 women, who underwent a total of 67 cycles (median 3.5; range 1-15). Nine patients had undergone prior systemic therapy consisting of interferon-alpha in 3, interleukin-2 in 1, interferon-alpha plus interleukin-2 in 4, and investigational therapy with bryostatin-1 in 1. There were 14 patients assessable for response (one withdrew), and no responses were seen. Median time to progression was 9 weeks (range 1-45). There were 3 patients (21%) who had stable disease for 18, 39, and 45 weeks. Hematologic toxicity was mild. Three patients had grade 3 or 4 gastrointestinal toxicity, and 3 required dose reductions. There were 2 early deaths, including 1 patient with pulmonary edema and 1 with hypotension. The study was terminated because there were no responses in the first 14 assessable patients, indicating that the response rate was likely to be less than 20%. We conclude that single-agent capecitabine has minimal activity for the treatment of metastatic RCC.