606 Background: Sentinel node navigation surgery (SNNS) is a standard technique to identify lymph node metastases in clinically node-negative breast cancer. However, the dye and radiopharmaceuticals for lymphatic mapping commonly used in Western countries are not available in Japan. Methods: To assess the optimal lymphatic mapping and the outcome after SNNS, the Japanese society for SNNS conducted a non-randomized multi-center prospective study on SNNS in early breast cancer. Primary endpoint is to evaluate the success rates and adverse events associated with various lymphatic mapping and SNNS, and secondary endpoint is to observe the outcome of patients who underwent SNNS during 5 years. After the protocol was approved by institutional review board, SNNS had been registered between July 2004 and October 2005. Results: Fourteen hundred and sixty-eight cases had pre-registration from 65 investigators at 23 institutions. As 46 cases were withdrawn for some reasons and 11 cases were diagnosed as benign disease, 1,411 cases were finally entered in this study. Dyes used for lymphatic mapping were indigocarmine, indocyanin green, patent blue, and isosulfun blue, and radiopharmaceuticals were 99m-technetium-labelled tin colloid, human serum albumin, and phytate. In 19 cases, superparamagnetic iron oxide was used for MRI- guided SNNS. As of December 2006, 98% of clinical report forms were analyzed. Dye-guided SNNS was performed in 240 cases, radio-guided SNNS in 56 cases, and combined method in 1,016 cases. Overall success rate was 99%. SNNS alone was treated in 1,138 cases (82%) and SNNS followed by axillary lymph node dissection in 258 cases (12%). Breast-conserving surgery was undergone in 1,175 cases (85%) and total mastectomy in 217 cases (15%). Dye-induced allergic adverse events were not reported. Postoperative adverse events of bleeding, wound infection and seroma were observed in about 1 % of cases, respectively. Conclusions: Dye-guided and/or radio-guided SNNS proved reliable for lymphatic mapping in breast cancer. The prognosis of all cases will be observed until 2010. No significant financial relationships to disclose.