Sentinel lymph node (SLN) biopsy has evolved over the years to become one of the most useful tools in the treatment of melanoma. Large, multi-institutional studies have confirmed that in experienced hands it is an accurate, reliable technique to identify tumor in the draining lymph nodes. The complications of the procedure are low, and it is generally well tolerated. The presence of melanoma in the sentinel lymph node is the most important predictive factor in patients with intermediate thickness melanomas. In patients with thin melanomas (<1 mm), the incidence of a positive SLN is low. The choice to perform a SLN biopsy in these patients must be weighed with risk factors such as Clark level, ulceration, sex and mitotic rate. In patients with thick melanomas (>4 mm), most studies have supported the prognostic value of SLN status. Patients with desmoplastic melanomas have a high risk of local recurrence, but low risk of SLN metastasis if the pathology demonstrates a pure desmoplastic form. Younger patients have a higher incidence of positive lymph nodes, yet an overall more favorable prognosis compared to older patients. Patients should understand that this procedure remains primarily a staging tool, as large prospective randomized trials have not demonstrated an overall survival benefit.