We report a case of breast carcinoma with repeated recurrences in the right bone. The recurrent site of the bone was treated by radiation therapy with a total of 3 7. 5 Gy irradiation, and chemotherapy with the CMF regimen. After 2 years, recurrence was suspected in the same region because there was an elevation of the NCC-ST-439 tumor marker. We carried out chemotherapy with S-1 100mg/body/day. The NCC-ST-439 value returned to within the normal range after 3 months' administration of S -1, and continued in the normal value for 20 months.