Breast cancer is the most common malignancy in women in the United States and is second only to lung cancer as a cause of cancer death. The overall management of breast cancer includes the treatment of local disease with surgery, radiation therapy, or both, and the treatment of systemic disease with cytotoxic chemotherapy, endocrine therapy, biologic therapy, or combinations of these. This article outlines the NCCN Guidelines specific to breast cancer that is locoregional (restricted to one region of the body), and discusses the management of clinical stage I, II, and IIIA (T3N1M0) tumors. For NCCN Guidelines on systemic adjuvant therapy after locoregional management of clinical stage I, II and IIIA (T3N1M0) and for management for other clinical stages of breast cancer, see the complete version of these guidelines at NCCN.org.