Microcapsules containing cisplatin were administered into the renal artery of mongrel dogs. Significant increase of the platinum tissue concentration in the kidney was observed 17 days after administration compared to injection of cisplatin only. The highest drug tissue levels were obtained when the renal artery was ligated after microcapsule injection. In addition the decrease in plasma levels indicated that microencapsulation causes, at least, a 100-fold enhancement of the ratio: exposure of infused tissue to the drug over total body exposure. On the contrary, no major change in drug urine excretion could be related to microencapsulation.