Clinical trials of UFT have been conducted on patients with far-advanced renal cell cancer with distant metastasis. All patients had evaluable lesions which had shown no change or progressive disease under prior therapy. Five of these cases had received Interferon as prior therapy. Thus far, the antitumor effects of the drug were evaluated in 8 cases according to the criteria proposed by the Koyama-Saito group. Partial response was obtained in 3 of 8 patients (37.5%). Two patients showed no change and three patients showed progressive disease UFT caused anemia and diarrhea in each of patients. To measure the 5-FU level in the tumor and normal kidney tissues UFT was administered at 600 mg per day on the day before radical nephrectomy in 2 patients, who had received embolization therapy of the renal artery prior to surgery. The 5-FU level was higher in tumor and normal kidney tissues than in serum, but there was no significant difference between tumor and normal kidney tissues. The embolization therapy of the renal artery may have been responsible for this result. UFT is one of the most useful drugs for the treatment of renal cell cancer.