BACKGROUND Merkel cell carcinoma (MCC) is a cutaneous neuroendocrine tumor that may spread via lymphatics and can therefore be staged with sentinel lymph node biopsy (SLNB). MCC is radiosensitive and chemosensitive, although the role of adjuvant therapy is still unclear. We examined the impact of different treatments on the outcome of MCC. METHODS We performed a retrospective review of state cancer registry data from California, Oregon, and Washington of patients diagnosed with primary skin MCC between 1988 and 2012 (n = 4,038). Data were analyzed using Cox regression and Kaplan-Meier methods to examine disease-specific survival. RESULTS Patients with positive nodes or no documented nodal evaluation had worse survival compared with node-negative patients. No nodal evaluation had decreased survival compared with lymph node evaluation by SLNB. Completion lymph node dissection conferred improved survival in patients with a positive SLNB. In clinically node-negative patients who had a positive SLNB, radiation and chemotherapy did not affect survival. CONCLUSIONS Lymph node evaluation is an important component to MCC treatment. The role of adjuvant radiation and chemotherapy needs further evaluation.