Objective: To discuss if the sentinel lymph node (SLN) biopsy is able to reflect the status of the axillary lymph node and the application of this technic in clinic. Methods: Using 99mTc-signed dextran, SLN-biopsy (SLNB) was carried out in 182 cases with breast cancer during May 1999 to September 2006. During the operation, γ-detector was used for orientation. After the SLNB, a modified radical mastectomy or breast conserving surgery were carried out to the patients, then a particular separate pathological examination of the SLN was made. Results: 178 cases of SLNB were carried out successfully, and the success rate was 97.8%, the out-checked SLN of each case ranged from 1 to 4, with an average of 2.5. All SLN was located at the first level of axilla, sensitivity of the SLNB was 93.4%, specificity was 100%, false negative rate was 6.6%, false positive rate was 0, accuracy was 97.8%, positive predictive value was 100.0%, negative predictive value was 96.7%, and Youden’s index was 0.934. Immunohistochemical examination was carried out in 59 cases of SLN, and 14 cases showed the existences of micro-metastasis, however, metastasis had not been found in non-SLN of these cases. Conclusion: SLN is able to reflect the metastasis of the axillary lymph node, and this can suggest the necessity of the axillary dissection in clinic. The SLNB using the isotope-tracer technic is simple and accurate. Methods: Using 99mTc-signed dextran, SLN-biopsy (SLNB) was carried out in 182 cases with breast cancer during May 1999 to September 2006. During the operation, γ-detector was used for orientation. After the SLNB, a modified radical mastectomy or breast conserving surgery were carried out to the patients, then a particular separate pathological examination of the SLN was made. Results: 178 cases of SLNB were carried out successfully, and the success rate was 97.8%, the out-checked SLN of each case ranged from 1 to 4, with an average of 2.5. All SLN was located at The first level of axilla, sensitivity of the SLNB was 93.4%, specificity was 100%, false negative rate was 6.6%, false positive rate was 0, accuracy was 97.8%, positive predictive value was 100.0%, negative predictive value was 96.7% , and Youden’s index was 0.9 34. Immunohistochemical examination was carried out in 59 cases of SLN, and 14 cases showed the existences of micro-metastasis, however, metastasis had not been found in non-SLN of these cases. Conclusion: SLN is able to reflect the metastasis of the axillary lymph node, and this can suggest the necessity of the axillary dissection in clinic. The SLNB using the isotope-tracer technic is simple and accurate.