Background : Management of the cervical lymph node is one of the most important factors to control head and heck carcinoma. We investigated the method of sentinel lymph node ( SLN ) detection for clinically positive neck metastasis. Methods : For 9 patients of tongue squamous cell carcinoma (N1: 5 cases, N2 : 4 cases, 5 males and 4 females), peritumoral perimucosal injection of Tc-99m -Rhenium colloid was performed, and followed by dynamic lymphoscintigraphy and hand-held gamma probe. All the patients underwent neck dissection, and after surgery we removed the lymph nodes from the resected tissue and measured the size and radioactivity. And then, examined metastasis in each lymph node pathologically. Results : In all cases, Rhenium colloid was accumulated in the lymph nodes ; identification rate was 100%. In most cases, accumulation was in the sub-mandible area and jugular chain. In 5 of 9 cases, it was accumulated in pathologically metastatic lymph nodes. But in the other 4 cases, it did not accumulate in the lymph node metastasis, which was distinguished clinically. In 2 cases, Rhenium colloid accumulation was detected in the contralateral lymph node. And in 1 case contralateral metastasis occurred where there was Rhenium colloid accumulation. Conclusion : When the sentinel lymph node had already metastasized and was blocked the lymphatic basin, injected colloid flowed to a different lymph node through another basin. We call this node "secondary SLN". We suggest detection of colloid in secondary SLN is useful for selecting the field of the neck dissection.