This review will address: (1) 'what are the current indications for radiation therapy (RT), following both mastectomy and breast-conserving surgery?' and (2) 'if RT is indicated, what are the appropriate volumes or 'targets' to be treated?' Given the complexity of these questions, this review will focus on selected topics considered of greatest current interest. In addition, this review will primarily focus on results obtained from randomized clinical trials (RCTs). Finally, we acknowledge an American point of view in our discussion.