The treatment effect of "ryu-wei-ti-huang-wan', a Chinese prescription composed of extracts from six plants, on diabetic impotence was evaluated in the present study. Adult male Wistar rats were divided into three groups: (1) rats rendered diabetic with a single intraperitoneal injection of streptozotocin (60 mg/kg body weight); (2) rats with streptozotocin-induced diabetes treated with a ryu-wei-ti-huang-wan powder preparation at a dose of 30 mg powder/kg body weight twice a day, and (3) control rats. A male rat was caged with an adult ovariectomized female rat during the dark cycle. Infra-red-light-illuminated video recording was utilized to evaluate the sexual performance. The diabetic rats exhibited depressed mounting activity and no intromission or ejaculation. After ryu-wei-ti-huang-wan treatment either for 1 day or 2 weeks, the diabetic rats showed significant improvement in mounting performance with preservation of intromission and ejaculation. No significant difference in the blood sugar level was noted between the treatment and non-treatment groups. In conclusion, the diabetic rats showed impairment in sexual arousal, erectile as well as ejaculatory functions. Ryu-wei-ti-huang-wan was effective in preserving these functions with a rapid onset. It is evident that the extracts exert the therapeutic effects not through a lowering of blood sugar. These substances are potentially useful in the clinical treatment of male diabetic impotence.