Data from the Surveillance, Epidemiology, and End Results program and the European Concerted Action on survival and Care of Cancer Patients (EUROCARE) project indicate that approximately 6% of women newly diagnosed with breast cancer have stage IV disease, representing approximately 12 600 new cases per year in the United States in 2005. Historically, local therapy of the primary tumor in this setting has been aimed solely at symptom palliation. However, several studies suggest that surgical excision or exclusive irradiation of the primary tumor can prolong these patients' survival. In contrast, the impact of surgical dissection of regional lymph nodes and postoperative radiotherapy is poorly documented, and the patient subgroups most likely to benefit from treatment of the primary tumor remain to be identified. Two prospective studies are currently examining the benefits of locoregional therapy compared with systemic therapy alone in this setting. Here, we discuss current issues regarding treatment of the primary tumor in breast cancer patients with synchronous metastases.