Objective: To investigate the clinical application of the detection of HER-2 gene by lfuorescence in situ hybridization (FISH) in breast cancer and the correlation between HER-2 gene ampliifcation and clinicopathology of breast cancer. Methods:Parafifn-embedded breast inifltrating ductal carcinoma from 48 patients were detected by FISH and immunohistochemistry (IHC) respectively for comparing the results of two methods. Results: HER-2 protein expressions were classified into three groups (3+/2+/1+ or 0) and the positive rates of HER-2 gene ampliifcation by FISH were 77.8%, 57.1% and 10.5%, respectively. Of the 29 cases with positive axillary lymph node, 12 were with HER-2 gene ampliifcation (P<0.05). Of the 10 cases with negative estrogen receptor (ER) and progesterone receptor (PR), 7 were with HER-2 gene ampliifcation (P>0.05). Conclusion:The false positive and negative rates are higher in HER-2 protein expression by IHC. Compared with IHC, FISH, being more effective and precise, can be applied extensively in clinic. HER-2 gene ampliifcation is conced with axillary nodes metastases.