Acanthopanax sessiliflorus SEEM extracts(AS) have been used to treat patient with diseases including cancer in Oriental countries. Recently, AS was known to have anti-cancer and immuno-stimulating activites. For these reasons, we investigated the effects of AS following gamma-ray irradiation on cytotoxicity for solid tumor cell line (S-180) and immune-potentiating ability such as proliferation of thymocytes and splenocytes. Finally we also investigated tumor weight and survival rate in tumor bearing mice. In our results, Treatment with AS suppressed proliferation of solid tumor cells (S-180) effectively. Treatment with AS accelerated thymocyte and splenocyte proliferation in tumor bearing mice. In addition, Treatment with AS reduced tumor weight and prolonged life of tumor bearing mice. In conclusion, we demonstrate that AS following gamma-ray irradiation is useful to treat patients with cancer, and also demonstrate that AS have both direct cytotoxic ability for cancer cells and indirect immune-stimulating action for thymocytes and splenocytes.