The response rate to chemotherapy for treating renal cell carcinoma is less than 20%.1) Renal cell carcinomas are normally located unilaterally in the kidneys, and accordingly renal arterial administration has been studied to deliver anticancer drugs to the unilateral kidney.2) When a drug is administered systemically, however, it is distributed throughout the whole body via the blood stream, leading to inadequate drug delivery to the target organ. We have described the kidney-and site-selective delivery of 5-fluorouracil (5-FU) by the application of 5-FU to the kidney surface in rats.