The cortex and root of Acnthopanax sessiliflorus, a herbal medicine, have been used for several diseases including cancer in Oriental countries. In the previous study, we showed that the cortex of this plant have anti-cancer activity. But its therapeutic efficacy of CORTEX ACANTHOPANAX RADICIS (CAR) is not clarified. For these reasons, we investigated immuno-potentiating and anti-cancer properties of CAR compared with CA, in terms of body and tumor weights, proliferation of thymocytes and tumor cells, and nitric oxide production from macrophages through in vitro and in vivo studies. In our results, administration of CAR reduced tumor mass and increased body weights. CAR also inhibited proliferation of tumor cells in vivo and in vitro dose-dependently. Thymocyte proliferation was accelerated by treatment with CAR and NO production was also promoted by CAR in vivo and vitro. In conclusion, we demonstrated that CAR is useful to treat for cancer as complementary or alternative medicine to Western medication, its therapeutic efficacy is involved in direct inhibition of tumor growth and immuno-potentiating activity.