Sentinel lymph node biopsy (SLNB) emerged in the 1990s as a new technique in the surgical management of the axilla for patients with early breast cancer, resulting in lower complication rates and better quality of life than axillary lymph node dissection (ALND). Today SLNB is firmly established in the armamentarium of clinicians treating breast cancer, but several questions remain. The goal of this paper is to review recent work addressing 4 questions that have been the subject of debate in the use of SLNB in the past few years: (a) What is the implication of finding micrometastases in the sentinel nodes? (b) Is ALND necessary in all patients who have a positive SLNB? (c) How accurate is SLNB after neoadjuvant therapy? (d) Can SLNB be used to stage the axilla in locally recurrent breast cancer following breast surgery with or without prior axillary surgery?