Breast cancer surgery continues to become more conservative. Supporting this conservatism are (1) earlier diagnosis through mammographic screening, (2) an increasing role for diagnostic ultrasound and magnetic resonance imaging, (3) the further development of image-guided core-needle biopsy, and (4) the advent of sentinel lymph node biopsy as an alternative to conventional axillary dissection. For patients with duct carcinoma in situ, the addition of radiotherapy and tamoxifen to surgical excision reduces local recurrence but has not yet improved survival over the rate observed with excision alone. There may be low-risk subgroups of duct carcinoma in situ patients for whom conservative surgery alone is adequate treatment. For patients with invasive cancer, breast conservation remains underutilized. A small survival benefit from post-mastectomy adjuvant radiotherapy is offset by an increased incidence of cardiovascular mortality, a phenomenon which has not yet been demonstrated for radiotherapy following breast conservation. Sentinel lymph node biopsy represents a new standard of care for axillary lymph node staging in the large majority of breast cancer patients with high-risk duct carcinoma in situ and stage I-II invasive cancers. The procedure is feasible, accurate, and works best with a combination of blue dye and radioisotope mapping. After proper validation studies, patients with negative sentinel lymph nodes do not require axillary dissection. The prognostic significance of sentinel lymph node micrometastases identified by enhanced pathologic techniques remains a matter of debate. Prophylactic mastectomy reduces breast cancer incidence and mortality among those with a high-risk family history, and mutations of BRCA1-2, but has significant adverse psychosocial sequelae for a small and unpredictable fraction of patients and should not be undertaken lightly. Prophylactic oophorectomy should be offered to all women with BRCA1-2 mutations, especially those beyond the years of childbearing.