From September 1979 through March 1981, a total of 302 patients with gastric cancer and undergoing gastrectomy at the Department of Surgery at Chiba University Hospital and its 14 affiliated hospitals was studied for clinical effectiveness of immunotherapy with Nocardia rubra cell wall skeleton. The patients were stratified by gross stage of cancer and degree of operative curability. They were then assigned randomly to either chemotherapy group or chemotherapy plus immunotherapy group. Immunotherapy used was intradermal injection of 400 micrograms of N. rubra cell wall skeleton which was given weekly for the first month and monthly thereafter. After the specimen was examined microscopically, the patients were classified by histological stage of cancer and radicality of surgical intervention into curative or noncurative groups. The patients were surveyed for survival period in December 1981. The postoperative survival rate was compared in patients of histologically curative or noncurative resection cases between the two treatment groups. No statistical difference was detected between the groups in age, sex, or operative procedures that might influence the patient's survival. As a result, statistical intergroup difference in survival rates was not seen in patients of the curative group, probably due to a short observation period. However, the intergroup difference in survival rates was statistically significant in patients of the noncurative group (p less than 0.01). These results indicate the adjunctive effect of N. rubra cell wall skeleton as an immunotherapeutic agent in patients undergoing gastrectomy for gastric cancer.