The medical management of invasive breast cancer has evolved based on the recognition that surgery alone was associated with few long-term cures. This Update will review the current status of breast cancer medical management in three areas: prevention in individuals with an elevated risk, adjuvant (postoperative) treatment of early breast cancer, and treatment principles in metastatic disease. Tamoxifen has emerged as a promising agent in the treatment of women at an increased risk for breast cancer and in those with in situ disease. However, the risks of treatment must be carefully weighed against the benefits in these cohorts of women with an excellent overall prognosis. This same principle can be applied to the use of adjuvant treatment in early invasive breast cancer, where the goal is cure. Adjuvant polychemotherapy is recommended in women considered at high-risk for relapse and death. In addition, women with hormone-sensitive breast cancer are offered adjuvant taxmoxifen. Nonetheless, there are some patients with low-risk disease or those with significant co-morbidities that are unlikely to benefit from adjuvant therapies and likely to sustain toxicities. The treatment goal in metastatic breast cancer is focused on palliation of symptoms as fewer than 10% of such patients achieve 5-year survival. However, novel targeted therapies are changing the treatment armamentarium and hold great promise. These new directions of treatment will be discussed as well as areas of controversy.