BACKGROUND The authors updated their experience with sentinel lymph node (SLN) biopsy of clinically node negative (N0) melanoma to clarify indications, predictive factors, and outcomes. METHODS A review of patients from the authors' institution's prospective database (n = 397) was performed; survival statistics were obtained from the institutional tumor registry. RESULTS The SLN-positive (SLN+) rate was 16% (47 of 282) for lesions >1 mm thick; only 2 of 105 T1 lesions were SLN+. Thickness >2 mm, upper extremity primary, and ulceration predicted SLN+ status. Most SLN+ patients underwent completion node dissection; 12% had additional positive nodes. The false-negative SLN biopsy rate was 4.0%; the majority involved lower extremity and head and neck primaries. The overall complication rate was 26%; all were minor and resolved within 6 months. Overall 5-year survival rates were 73% and 92% for SLN+ and SLN-negative patients, respectively. SLN status was the most significant predictor of survival. CONCLUSIONS SLN status, the most important determinant of outcome for clinically N0 melanoma, correlated with T stage, ulceration, and site. Staging of T1 lesions had low yield. A minority of completion node dissections yielded additional positive nodes.