The sentinel lymph node (SLN) is the lymph node that represents the 'gate-keeper' of the lymphatic basin; it is the first node to receive lymphatic drainage from the site of the primary tumor. SLN biopsy is a staging procedure and should be considered as such; it is not meant to be a therapeutic operation. The SLN can be mapped and biopsied using tracer agents (e.g. radiolabelled colloid and/or vital blue dye), which are injected around the primary tumor site. Pathologic analysis of the SLN using a combination of serial sectioning of the node, standard hematoxylin and eosin staining, and immunohistochemistry decreases the false-negative rate compared with traditional nodal processing. SLN biopsy is associated with lower morbidity than full lymphadenectomy. The SLN technique accurately reflects the metastatic status of the regional lymph-node basin; recurrent nodal disease in the mapped basin is rare following a tumor-free SLN biopsy result. The objectives of this review are to provide a current and concise overview of the current literature on SLN biopsy and describe its role in clinical oncology.