In 156 cases of gastric cancer, levamisole (LMS) was administered at a daily dose of 150 mg for three consecutive days every other week. The administration was started 3 days before operation. This medication was repeated for more than one month. The survival rate up to two years after surgery was studied. The survival rate was not affected in patients with Stage I and II gastric cancer, but in patients with Stage III, the difference in the survival rate between the LMS group and the control group was significantly higher than that in the control group (p less than 0.05). In patients with Stage IV, the survival rate in the LMS group was higher than that in the control group although the difference was not significant. In patients of Stage III and IV, the effect of LMS on the survival rate was highest in cases with curative resection (p less than 0.01). In cases with noncurative resection, the difference between the LMS group and the control group was greatest (24.4%) 12 months after surgery but not significant (p less than 0.5), and also in cases without resection the difference between the two groups was greatest (20.3%) 12 months after surgery but not significant (p less than 0.2).