Sentinel lymph node biopsy (SLNB) is a widely accepted staging procedure in patients with melanoma. However, it is unclear which factors predict the occurrence of micrometastasis and overall prognosis and whether SLNB should also be performed in patients with thin primary tumors. At our Department of Dermatology, University of Munich (Germany), 1049 consecutive melanoma patients were identified for SLNB between 1996 and 2007, and were followed-up to assess disease-free and overall survival. Of those, a total of 854 patients were analyzed prospectively. Patients with positive SLN were subjected to selective lymphadenectomy. The association of patient characteristics with SLN was assessed by multivariate logistic regression. Survival curves were performed using the Kaplan-Meier method. Cox proportional hazard regression with different adjustments was used to estimate the effect of SLN on survival. The detection rate of SLN was 97.24%, of which 24.9% were metastatic. Significant parameters upon SLN positivity were tumor thickness and nodular type of melanoma. The 5-year overall survival was 90.1 and 58.1% in SLN-negative and SLN-positive patients, respectively. Upon multivariate analysis tumor thickness and SLN status were significant factors influencing both disease-free survival and overall survival. In conclusion, our data confirm that SLNB is relevant as a diagnostic and staging procedure and that tumor thickness is of predictive importance. SLN status should be taken into account when designing clinical trials and informing patients about the probable course of their disease. Our data suggest that in case of a nodular melanoma subtype SLNB should also be considered at a tumor thickness below 1 mm.