The value of cyclophosphamide/methotrexate/5-fluorouracil (CMF)-type regimens in surgical adjuvant therapy in certain subsets of patients with axillary lymph node-negative breast cancer has been evaluated in Europe and the USA. However, Japan has a distinctive standpoint regarding the indications for surgical adjuvant chemotherapy for breast cancer patients. In addition, oral fluoropyrimidines are widely used to treat breast cancer patients in both adjuvant and metastatic settings due to their low toxicity and convenience for long-term administration. Although the antitumor activity and the ability to prolong disease-free survival times of oral fluoropyrimidines have been evaluated in patients with breast cancer, available data are not sufficient to justify replacing CMF-type regimens with oral fluoropyrimidines in postoperative chemotherapy for breast cancer patients. To evaluate the utility of oral fluoropyrimidines in surgical adjuvant chemotherapy, the National Surgical Adjuvant Study Group (N-SAS) was founded in 1995 as a government-funded research group, and nationwide multiinstitutional trials were designed for breast cancer as well as colon and gastric cancers. For high-risk, node-negative breast cancer patients, a prospective randomized trial of surgical adjuvant chemotherapy comparing 6 cycles of CMF with 2 years of daily uracil/tegafur (UFT) started in October 1996. The endpoints of this study include disease-free and overall survival, adverse reactions, quality of life, and cost.