Cordyceps militaris(CM) has been used as a traditional folk medicine to strengthen the immune system and regain energy for hundreds of years in Far East Asian countries. In the present studies, we determined that the stimulatory effect of Cordyceps militaris on testosterone production in male mouse rats. Results illustrated that changes of the body weight, food and water intake of the rats were not observed in this study but the concentration of testosterone in the serum of the rats was significantly increased by CM(p < 0.05). Therefore fruiting bodies of CM grown on the drone bee medium may be an integrative medicine for the treatment of reproductive problems caused by insufficient testosterone levels in human males.