Approaches for breast cancer treatment are invasive, disfiguring, have significant side-effects, and are not always curative. Nanotechnology is an emerging area which is focused on engineering of materials <100 × 10−9 m. There is significant promise for advancing nanotechnology to improve breast cancer diagnosis and treatment including non-invasive therapy, monitoring response to therapy, advanced imaging, treatment of metastatic disease, and improved nodal staging. Current approaches and important future directions are discussed. J. Surg. Oncol. 2011; 103:317–325. © 2011 Wiley-Liss, Inc.