Intra-operative sentinel lymph node (SLN) mapping and biopsy is a procedure that accurately stages the regional lymph node basin. Defined patterns of lymphatic drainage allow intra-operative determination of the first (sentinel) lymph node in the regional basin, and the absence of metastatic disease in the SLN accurately reflects the absence of melanoma in the remaining regional nodes. The use of a radiocolloid and a handheld gamma probe together with a vital blue dye provides optimal results, and allows for the successful identification of the SLN(s) in over 98 percent of the procedures. Close collaboration between surgeons, nuclear radiologists and pathologists is required to ensure optimal results. Surgical excision of the SLN allows for a more thorough and focused pathological examination of one or two nodes. Examination of serially sectioned SLNs by H&E staining, immunohistochemical staining and perhaps RT-PCR should reduce the number of patients with missed microscopic melanoma in the regional lymph nodes. Recently reported survival data from the Intergroup Melanoma Trial suggest that patients may benefit from identification and removal of regional lymph nodes that contain metastatic melanoma. Furthermore, the survival benefit recently reported in patients with melanoma metastatic to regional nodes prospectively randomized to receive high dose Interferon alfa-2b signals that the surgeons should aggressively examine patients for the presence of occult regional melanoma metastases. Intra-operative SLN mapping and SLN biopsy is a cost-effective procedure that allows accurate identification of regional lymph nodes that contain metastatic melanoma.