Cordyceps (summer-grass and winter-worm) is one of the most valued traditional Chinese medicines used for the replenishment of body health. It consists of the dried fungus Cordyceps sinensis growing on caterpillar larva Hepialus armoricanus. The extract of the fruiting body (fungus) and the worm (caterpillar) has been reported to have anti-oxidant, anti-viral and anti-tumor activity. In the present study, we examined and discussed the effect of the extracts from the fruiting body and worm of Cordyceps on cell growth and protein expression in a human breast cancer cell line.