A revolution is challenging the dogma that local treatment for all patients with breast cancer treated with breast conservation therapy must include postoperative radiotherapy delivered to the whole breast. Such prolonged postoperative radiotherapy is a burden to patients and hospitals and forces many women to chose mastectomy instead. Furthermore, for patients receiving chemotherapy, the start of conventional radiotherapy may be delayed so long as to increase the risk of local relapse. These problems might be eliminated if effective radiotherapy could be given as a single treatment intraoperatively, immediately after the surgery. Local recurrence after breast-conserving surgery usually occurs in the portion of the breast in the immediate proximity of the tumor, even when radiotherapy is omitted. Therefore, it should usually be possible to restrict radiotherapy to only the area adjacent to the tumor in selected women. Based on this premise, we have devised a new technique of partial breast irradiation, with the intention of completing all local treatment in a single session. In this article, we elaborate on the rationale and on the different methods of delivering intraoperative radiotherapy. If this approach is validated in ongoing randomized trials, it could save time, money, and breasts.