Cisplatin is one of the most effective antitumor agents currently available for cancer therapy. However, its clinical use has been limited by its severe side effects, especially nephrotoxicity. Therefore, brazilin, which has a radical scavenging effect, was given intraperitoneally to evaluate the effect on cisplatin nephrotoxicity in rats. Remarkable protective effects against nephrotoxicity of cisplatin were observed when brazilin was administered to rats simultaneously with cisplatin. Hepatotoxicity induced by combination treatment of cisplatin and brazilin was evaluated by measuring serum glutamic pyruvate transaminase and serum glutamic oxalate transaminase. Combination treatment did not affect the levels of sGPT and SGOT, and any combination treatment did not induce metallothionein in kidney. Brazilin which has radical scavenging effect directly reduced nephrotoxicity of wisplatin in vivo. Thus, it seems that nephrotoxicity of cisplatin was caused by free radicals. The present results Indicate that brazilin, when it is given with cisplatin, may provide protection against cisplatin nephrotoxicity in rats.