The effects of immunotherapy such as PSK, Bestatine and OK-432 (oral administration) in combination with various chemotherapy were reviewed in the patients who underwent gastrectomy for gastric cancer from the Japanese references. The immunotherapy might lead to better prognosis about 10% or more, however, if it is administered for such a selected patient who show a lower preoperative serum IAP value (580 micrograms/ml), higher total protein (6.5g/dl), better performance status (0, 1 or 2) and etc, the survival rate could be increased. The usefulness of immunotherapy was also noted in such a case which showed severe side effects of chemotherapy and bad performance status. Moreover, the pre- and post-operative immunotherapy was advisable for prevention of surgical stress and enhancement of tumor metastases.