The effect of postoperative long-term chemotherapy was evaluated in 89 patients who were treated with daily oral administration of 600-800 mg of tegafur for 2 years after gastrectomized because of stage III stomach cancer in our department from 1975 to 1977. Other 128 patients, as control, were given no chemotherapy after undergoing an operation from April, 1967 to the end of 1974. The minimum, crude 5-year-survival rate in the group given chemotherapy was significantly higher (57.3%) than that in the control group (35.2%). Twenty-six patients without lymphnode metastasis and 36 patients with n1 (+) metastasis in the treated group showed significantly higher 5-year-survival rate of 77% and 64%, respectively compared to the control group (46% and 33%, respectively). The patients having n2 (+) metastasis in the treated group, however, showed no significantly higher 5-year-survival rate (30%) compared to the comparable patients in the control (17%). The 5-year-survival rate in 54 cases treated with the total dose of more than 200 g of the drug was 78%, whereas that in other 35 cases receiving lesser dose was 26%. Furthermore, 35 cases given more than 300 g of the drug showed the 5-year-survival rate of 88.6%. These data showed that a postoperative long-term chemotherapy with tegafur remarkably improved the 5-year-survival rate of the patients with stage III stomach cancer, especially when given for more than 18 months at the total dosis of more than 300 g.