The clinical effectiveness of immunotherapy with the cell wall skeleton of Bacillus Calmette-Guérin was assessed in a study involving 140 consecutive patients with gastric cancer, who were gastrectomized at a single institution from January 1976 through December 1978. These patients were randomized by an envelope method after operation and divided into three treatment groups: 'control', 'chemotherapy', and 'chemotherapy plus immunotherapy with BCG-CWS.' Only two patients who died during surgery were excluded, and a survey of survival periods was made on the remaining 138 patients in January 1982. As a result, statistically significant differences in the survival rate curve were observed between the control and chemotherapy plus immunotherapy groups (P less than 0.01), and between the chemotherapy and chemotherapy plus immunotherapy groups (P less than 0.05). These results emphasize effectiveness of BCG-CWS as an adjuvant immunotherapeutic agent in gastrectomized cancer patients.