[摘要]:Background: The optimum regimen and optimum duration of administration of postoperative chemotherapy would vary with the postoperative residual tumor volume. Whether or not prolonged administration of oral uracil/tegafur (UFT) with leucovorin (LV) would prolong the survival period was assessed experimentally. Materials and Methods: Murine models of pulmonary metastasis with different volumes of residual tumor after primary tumor resection were prepared, and the efficacy of 12-week and 4-week oral administration of UFT/LV as postoperative adjuvant chemotherapy was compared. Results: In the model with only a small volume of occult residual tumor after early resection of the primary tumor, the survival period in the 12-week UFT/LV group was significantly increased as compared with that in the untreated group, Whereas no significant difference was noted between the 4-week UFT/LV group and the untreated group. Conclusion: Long-term administration of UFT/LV as postoperative adjuvant chemotherapy may be potentially beneficial.