The efficacy of Bestatin as adjuvant immunochemotherapy for patients with resectable gastric cancer was investigated. Ninety-six patients with similar background factors were randomized into two groups; a control group and an experimental group, the patients in the experimental group receiving a daily oral dose of 60 mg Bestatin over a long period. All 96 patients were treated with a bolus intravenous injection of mitomycin C (MMC) plus oral administration of tegafur (FT-207, FT). The survival rate of the patients in the MMC + FT + Bestatin group was more favorable than that of the patients in the MMC + FT group, but the difference was not statistically significant. The survival rates of the MMC + FT + Bestatin group patients in the stratification of stage III + IV and positive histological serosal invasion, ps(+), were significantly superior to those of the MMC + FT group patients (Logrank test: p less than 0.05). Moreover, in patients with positive histological serosal invasion, the recurrence of peritoneal dissemination was significantly suppressed in the MMC + FT + Bestatin group.