Three hundred and twenty-two patients with locally advanced (stages III and IVA) and disseminated (stage IVB) gastric cancer were included in a randomized trial to assess the effect of immunochemotherapy (BCG and 5-fluorouracil,5-FU). The survival of patients receiving chemoimmunotherapy was compared to chemotherapy (5-FU) or no further treatment (control) groups. Patients with stage III underwent radical surgery (subtotal or total resection), stage IVA palliative resection, while explorative laparotomy or bypass was performed in stage IVB. Patients with stage III and IVA receiving immunochemotherapy had significantly (p less than 0.05) prolonged survival in comparison to chemotherapy or control groups. Prolongation of survival was more pronounced in patients with diffuse type carcinoma than in patients with intestinal type of tumour according to Lauren's classification. The survival of patients receiving chemotherapy was somewhat shorter than that of the control group, but the differences were not statistically significant. There was no effect of either immunochemotherapy or chemotherapy in patients with stage IVB. No serious side effects of immunochemotherapy were noted. These results indicate that immunochemotherapy may be a safe form of adjuvant treatment in patients with operable gastric cancer.