PURPOSE: Radio-guided sentinel node biopsy has become a standard method for evaluating the axillary status. However, there is no guideline for the optimum extent of sentinel lymphadenectomy. The object of this study was to assess the probability of metastases according to the sequence of radioactivity in the sentinel nodes and to determine the accuracy of the methods for evaluating metastases. METHODS: 80 consenting patients underwent sentinel lymph node biopsy using 99mTc-phytate. All the lymph nodes that showed radioactivity higher than surroundings were excised and labeled as SN1 to SN5 according to the sequential radioactivity. All the excised sentinel nodes were evaluated by frozen sectioning (FS) and permanent sectioning (PS). The sensitivity, specificity, negative predictive value and accuracy of the procedure were then analyzed according to the evaluation method. RESULTS: All 80 patients showed a variable number of axillary sentinel node sites (SN1-SN5) and 19 patients (23.8%) had three or more sentinel node sites, with an average number of 1.98. The sensitivity, specificity, NPV and accuracy were higher on PS (94.4%, 100%, 98.4% and 98.8% respectively) than on FS (88.9%, 100%, 96.9% and 97.5% respectively). 20 patients were found to have metastatic breast cancer within the sentinel lymph nodes by IHC, but one case of a metastatic, non-sentinel node was found in the 60 patients with negative sentinel nodes, so that the final false negative rate was 4.8%. In 18 of the 20 sentinel node-positive patients(90.0%), the most radioactive lymph node (SN1) was a positive node. The removal of the most radioactive sentinel node and the 2nd most radioactive sentinel node accurately staged all 20 sentinel node-positive patients. CONCLUSION: Careful evaluation of the sentinel nodes with FS, PS and IHC study is essential to reduce the false negative results. In addition, excision of the highest and the 2nd highest lymph nodes is essential and the excision of the 3rd highest node if any, should also be considered for obtaining a better treatment results.