The role of radiation therapy in the management of breast cancer is well established. Questions remain, however, regarding: 1) which patients derive the most benefit from the addition of radiation in breast conservation for ductal carcinoma in situ (DCIS) and after mastectomy for node-positive invasive cancer; 2) what is the role of brachytherapy in the management of invasive disease, either as primary therapy or as a boost after external beam therapy; and 3) whether radiation fields can be modified given the low rates of local-regional recurrence reported after breast conserving therapy in patients receiving systemic therapy.