BACKGROUND: Sentinel node biopsy (SNB) may represent an alternative to elective neck dissection for the staging of patients with early head and neck squamous cell carcinoma (HNSCC). To date, the technique has been successfully described in a number of small single-institution studies. This report describes the long-term follow-up of a large European multicenter trial evaluating the accuracy of the technique. METHODS: A total of 227 SNB procedures were carried out across 6 centers, of which 134 were performed in clinically T1/2 N0 patients. All patients underwent SNB with preoperative lymphoscintigraphy, intraoperative blue dye, and handheld gamma probe. Sentinel nodes were evaluated with hematoxylin and eosin (H&E) staining, step-serial sectioning (SSS), and immunohistochemistry (IHC). There were 79 patients who underwent SNB as the sole staging tool, while 55 patients underwent SNB-assisted elective neck dissection. RESULTS: Sentinel nodes were successfully identified in 125 of 134 patients (93%), with a lower success rate observed for floor-of-mouth tumors (FoM; 88% vs. 96%, P = 0.138). Also, 42 patients were upstaged (34%); of these, 10 patients harbored only micrometastatic disease. At a minimum follow-up of 5 years, the overall sensitivity of SNB was 91%. The sensitivity and negative predictive values (NPV) were lower for patients with FoM tumors compared with other sites (80% vs. 97% and 88% vs. 98%, respectively, P = 0.034). CONCLUSIONS: Sentinel node biopsy is a reliable and reproducible means of staging the clinically N0 neck for patients with cT1/T2 HNSCC. It can be used as the sole staging tool for the majority of these patients, but cannot currently be recommended for patients with tumors in the floor of the mouth.