Objective : This study investigated the effects of Yangsaengwhallyukdan on nitrite oxide synthase (NOS) activity, nitrite level, antioxidation and erectile response in rat corpus cavernosum penis. Methods : Yangsaengwhallyukdan was formulated to contain various natural products that have been used to treat erectile dysfunction. Yangsaengwhallyukdan suspended in a 0.5% CMC solution was oral-administered, 50 mg or 100 mg per 1 kg of body weight for 30 days, while the normal group was administered only with a 0.5% CMC solution. The efficacy of the Yangsaengwhallyukdan was assessed with regard to erectile function. Results: After the Yangsaengwhallyukdan was administered to the rat for 30 days, the urethral NOS activity increased. The level of urethral nitrite, glutathione and testosterone increased too. The level of urethral lipid peroxide was decreased in Yangsaengwhallyukdan treated rats. The erectile response to a cavernous nerve stimulation in L-NAME$(10^4)$-treated rats in rats given Yangsaengwhallyukdan reached the level of the normal group. Conclusions : This study suggest that Yangsaengwhallyukdan is effective for the treatment of erectile dysfunction.