A randomized controlled study by envelope method was carried out with the purpose of evaluating effects and side effects of levamisole in patients with resectable stomach cancer. The patients were randomly allocated to the treatment either with control or levamisole according to the indication of the envelope opened at least 3 days prior to surgery. The control group was treated with Mitomycin C (day 0, 20 mg day 1, 10 mg, one shot i.v.) and 5-FU(150 mg/day, p.o.). The levamisole group was treated with Mitomycin C, 5-FU and levamisole. Levamisole was administered at a daily dose of 150 mg for 3 consecutive days before surgery, and the 3 consecutive days administration schedule was repeated every fortnight for one year after surgery. Four hundred and forty-six patients were entered in this trial. However, with the exclusion of 104 patients as exceptions and dropouts, the total eligible patients were 342, consisting of 167 in the control group and 175 in the levamisole group. The effects were evaluated by comparing the disease-free interval or the survival time of both groups. There was no significant difference in the disease-free interval and survival. In this study, we have not yet reached the conclusion that levamisole is effective in prolonging disease-free interval and survival time, because high survival rates are still maintained in both groups for 2 years after surgery. The final conclusion would be drawn with the follow-up results in the future.