In order to evaluate the combination of immunochemotherapy with mitomycin C (MMC), futraful (FT) and PSK, as an adjuvant to surgery for curatively resected gastric cancer, a randomized controlled study by the sealed envelope method was performed with the participation of 97 hospitals in the Kyushu and Chugoku districts of Japan. The MMC + FT + PSK group showed a significant increase in 5 year survival from the other groups (p less than 0.05). Moreover the survival rate was significantly higher in the MMC + FT + PSK group than in the MMC + FT group (p less than 0.01). According to the analysis on stratification, the MMC + FT + PSK group showed the best survival rate in cases with positive lymph node metastases, positive serosal invasion and positive lymph node metastases plus serosal invasion, and in cases of undifferentiated carcinoma by histological type and in those with a preoperative positive PPD reaction (p less than 0.01 or p less than 0.05). Thus, the combination of MMC, FT and PSK was indicated to be useful as an adjuvant immunochemotherapy for those patients with gastric cancer submitted to curative resection.