During the past decade, improvements in treatment-planning tools, computer and imaging technologies, and new therapeutic modalities have allowed radiation to be delivered in a conformal fashion while minimizing treatment toxicity. It is important that physicians involved in breast cancer treatment recognize the numerous advances that have occurred in the delivery of radiation therapy. Changes in 3 specific areas in treatment planning and delivery have revolutionized the way we approach breast cancer treatment: the design of radiation fields using computed tomography (CT) data sets, the development of 3-dimensional dose-calculation algorithms, and the development of new methods to modulate the delivery of radiation dose. With the advent of CT simulators, individual patient anatomy and pathology can be readily visualized and reconstructed in axial, coronal, and sagittal views. With an improved anatomic delineation between the target volumes and critical organ structures, the treatment fields can be designed to be more congruous to the areas at highest risk. In the past few years, new 3-dimensional dose-calculation algorithms have been generated that more accurately calculate dose distributions throughout the treatment-planning volume. Finally, modern linear accelerators allow for modulation of the dose intensity of the radiation beam, which may lead to improved aesthetics and decreased side effects while ensuring that the volumes at high risk receive the prescribed dose. Radiation therapy can be delivered safely and effectively to patients with breast cancer.