A total of 48 patients with gastric cancer were randomly assigned to receive either endoscopic injections of OK-432 plus systemic treatment with intravenously administered 5-fluorouracil and intradermally injected OK-432 (group A) or systemic therapy alone (group B). Morphologic improvement occurred in 7 of the 22 patients in group A. In one patient the tumor mass disappeared completely. In group B morphologic improvement occurred in only 2 of the 26 patients. The survival rate throughout the 24-month period was significantly (P less than 0.01) higher in group A than in group B patients. Thus, local administration of OK-432 by endoscopic injection is effective and is recommended for the treatment of patients with advanced gastric cancer.