A controlled clinical trial of surgical adjuvant immunochemotherapy of gastric cancer was started in July, 1974 involving twelve institutes (Chairman; T. Kondo) in Japan. Patients with gastric cancer undergone curative resection were eligible. These patients were divided into 3 groups; Group A, mitomycin C (MMC) + 5-fluorouracil (5-FU): Group B, MMC + 5-FU + PSK or MMC + 5-FU + OK-432; and Group C, surgery alone. Of 1412 patients accumulated up to December 1977, 848 cases were evaluable: Group A-264 cases, group B-290 and group C-294. Side effects such as leukopenia, thrombopenia, elevated GOT and GPT, albuminuria and digestive disorders, were observed in 54 cases (20.5%) of group A and in 59 cases (20.3%) of group B. The 3-year survival rates of total cases were 79.2% with group A, 77.0% with group B and 85.2% with group C. The 2-year survival rates of histological stage II cases were 93.4% with group A, 90.5% with group B and 80.7% with group C. The difference in survival rate between A and C (12.7%) was statistically significant (p less than 0.05). The efficacy was not related to the histological type of gastric cancer. Adjuvant immunochemotherapy using OK-432 was significantly effective on a 1-year survival rate of stage IV gastric cancer.