Radiation therapy plays a critical role in the management of breast cancer and often is unavailable to patients in low- and middle-income countries (LMCs). There is a need to provide appropriate equipment and to improve the techniques of administration, quality assurance, and use of resources for radiation therapy in LMCs. Although the linear accelerator is the preferred equipment, telecobalt machines may be considered as an acceptable alternative in LMCs. Applying safe and effective treatment also requires well trained staff, support systems, geographic accessibility, and the initiation and completion of treatment without undue delay. In early-stage breast cancer, standard treatment includes the irradiation of the entire breast with an additional boost to the tumor site and should be delivered after treatment planning with at least 2-dimensional imaging. Although postmastectomy radiation therapy (PMRT) has demonstrated local control and overall survival advantages in all patients with axillary lymph node metastases, preference in limited resource settings could be reserved for patients who have ≥4 positive lymph nodes. The long-term risks of cardiac morbidity and mortality require special attention to the volume of heart and lungs exposed. Alternative treatment schedules like hypofractionated radiation and partial breast irradiation currently are investigational. Radiation therapy is an integral component for patients with locally advanced breast cancer after initial systemic treatment and surgery. For patients with distant metastases, radiation is an effective tool for palliation, especially for bone, brain, and soft tissue metastases. The implementation of quality-assurance programs applied to equipment, the planning process, and radiation treatment delivery must be instituted in all radiation therapy centers. Cancer 2008;113(8 suppl):2305–14. © 2008 American Cancer Society.