Combined chemotherapy including 5-FU plus radiation treatment resulted in a synergistic effect has been reported. S-1 enhances a radiation response of colon cancer cell line xenografts. Also the effectiveness of S-1 + radiation therapy has been reported. A 66-year-old man underwent a low anterior resection for lower rectal cancer. Adjuvant chemotherapy was not performed due to Stage II rectal cancer. Twenty months after the operation, solitary sacral bone metastasis was found during the postoperative work-up. S-1 (120 mg/day) combined with radiotherapy was performed on days 1-14 and 21-35. Radiation (3 Gy) was administered a total of 45 Gy on days 1-5, 7-12 and 35-40. Moreover, the reduction was judged as complete response after 11 courses of mFOLFOX 6. There has been no sign of recurrence for 44 months. It suggested that local control therapy (S-1 + radiation) plus systemic chemotherapy (mFOLFOX6) was one of the promising effective therapies for single sacral bone metastasis of rectal cancer.