Short-course radiotherapy for the whole breast after breast conserving surgery is an alternative to conventional fractionation schedules for radiotherapy. This method shortens the treatment period by increasing the daily fraction dose from 2 to 2.5 Gy or more, and is already being used in Canada and parts of Europe as a more convenient treatment for breast cancer patients than conventional long-term radiotherapy. An important randomized trial in Canada found that there were no statistical differences in efficacy or adverse effects between conventional radiotherapy and short-course radiotherapy. However, that trial included only breast cancer patients with the most favorable prognoses and excluded patients who had carcinoma involving the inked margin of excision. In that trial, additional boost irradiation to the lumpectomy site was not used, and only 11% of patients were treated with systemic chemotherapy. It is also possible that irradiation using large fraction doses cause more severe late toxicities in normal breast tissue than conventional fraction irradiation. Therefore, while short-course radiotherapy may also prove more convenient, further clinical studies should be performed to confirm the feasibility of the new method for Japanese women, before being put into general clinical use in Japan. The present paper is a review of short-course radiotherapy for the whole breast after breast conserving surgery.