The progress and role of adjuvant therapy for resectable colorectal cancers are reviewed herein. 5-FU/leucovorin is considered the standard treatment in the postoperative adjuvant chemotherapy for Dukes'C colon cancer. The oral 5-FU prodrugs, such as UFT and capecitabine, will replace 5-FU infusion in the adjuvant chemotherapy in the near future. In Dukes'B colon cancer, the results of postoperative adjuvant chemotherapy are controversial. Many randomized trials in the USA and Europe have demonstrated that pre- or postoperative radiation therapy for rectal cancer decreases local recurrences but has no additional benefit on survival compared with 5-FU-based adjuvant chemotherapy. Adjuvant radiation therapy for rectal cancer is not widely used in Japan, while chemotherapy is considered the adjuvant treatment of choice. The local recurrences of rectal cancer is a surgeon-related phenomenon: the surgical technique used and the skill of the surgeon are major factors influencing outcome.