For older patients with clinically lymph node-negative breast cancer who have estrogen receptor-positive tumors and are treated with tamoxifen, randomized trials comparing axillary lymph node dissection (ALND) versus no ALND show that the omission of ALND improves patient quality of life and has no adverse effects on mortality. These results have served to justify sentinel node biopsy (SNB) omission in selected older patients with breast cancer. More recently, clinical trials were launched to assess SNB omission in younger patients, with recurrence and survival as the primary outcomes of interest. Three important considerations serve as the basis for these ongoing trials. First, it is assumed that SNB omission will improve patient quality of life, although, to date, there is no level I evidence to support this assumption. Second, axillary surgery has never been shown to reduce breast cancer mortality, but it does reduce the risk of axillary recurrences, although adjuvant systemic therapy and radiotherapy also reduce these recurrence risks. Finally, nodal status is losing importance as a guide for adjuvant systemic therapy decision making because these decisions are now increasingly predicated on tumor biomarkers and gene profiling, but it is gaining importance for adjuvant radiotherapy decision making. Because quality-of-life considerations are the primary motivation for abandoning SNB, there is a need for randomized trials comparing SNB versus no SNB/no axillary surgery, with quality of life as the primary end point (level I evidence). Moreover, suitable alternatives to guide adjuvant radiotherapy decision making will require validation before SNB omission can be justified for patients of all ages who have clinically nodenegative breast cancer.