Several studies suggest that melanoma patients with a positive sentinel node biopsy (SNB) can avoid having complete nodal dissection on the basis of pathological features of the node. The aim of the study was to determine the value of metastatic area ratio as a predictive factor for nonsentinel node (NSN) positivity. A retrospective analysis was carried out of melanoma patients who underwent SNB in a single institution between 2000 and 2010. A total of 697 patients were evaluated. In 155 patients (22.2%), the SNB was positive; 146 lymphadenectomies were performed, and 23 patients in whom this was performed (15.8%) had positive NSN. In multivariate analyses, Breslow thickness of more than 2 mm, perinodal vascular invasion, and metastatic area ratio were significantly related to NSN positivity in the complete nodal dissection. Metastatic area ratio of a positive SNB can be valuable in predicting the risk of NSN positivity.