Axillary node status is a major prognostic factor in early-stage disease. Traditional staging needs levels I and II axillary lymph node dissection. Axillary involvement is found in 10%–30% of patients with T1 (<2 cm) tumours. Sentinel lymph node biopsy is a minimal invasive method of checking the potential nodal involvement. It is based on the assumption of an orderly progression of lymph node invasion by metastatic cells from tumour site. Thus, when sentinel node is free of metastases the remaining nodes are free, too (with a false negative rate lesser than 5%). Moreover, Randomized trials demonstrated a marked reduction of complications associated with the sentinel lymph node biopsy when compared with axillary lymph node dissection. Currently, the sentinel node biopsy procedure is recognized as the standard treatment for stages I and II. In these stages, this approach has a positive node rate similar to those observed after lymphadenectomy, a significant decrease in morbidity and similar nodal relapse rates at 5 years. In this review, the indications and contraindications of the sentinel node biopsy are summarized and the methodological aspects discussed. Finally, the new technologic and histologic developments allow to develop a more accurate and refinate technique that can achieve virtually the identification of 100% of sentinel nodes and reduce the false negative rate.