The effect of postoperative adjuvant chemotherapy on survival rate of gastric cancer patients of Stage III was evaluated. Ninety-nine patients evaluated as Stage III according to the general rules for surgical studies on cancer of the stomach received surgical treatments at our Department in the period of 1967 to 1978. Patients were classified into following three groups: (A) no chemotherapy group (54 cases) (B) short term chemotherapy group (15 cases, receiving chemotherapy postoperatively for 20 days) (C) long term chemotherapy group (30 cases, more than 3 months postoperatively and more than 60 g of total dose of FT-207) Three-year survival rates of the patients were 40.7% in (A) group, 26.7% in (B) and 66.7% in (C), respectively. These results suggested that a long term postoperative chemotherapy significantly prolonged the survival times of gastric cancer patients in Stage III (C vs B: P less than 0.02, C vs A: P less than 0.03). On the other hand, a short term chemotherapy after surgery decreased the survival rate when comparing with no chemotherapy group, possibly due to impairment of host's anticancer immunity.