Abstract: Objective: To observe the relationship between expression of Her- 2 in breast cancer and clinicopathologic status. Methods: Data from 4773 primary breast cancer cases seen in Tianjin Cancer Hospital from July 2002 to November 2005 were collected. The age of patients ranged from 15 to 92 years old, and the median age was 50. All of the cases were confirmed as breast cancer by pathohistology. Expression of ER, PR, Her- 2, P53, and PCNA was measured by immunohistochemistry (IHC). Median follow- up period was 40 months. Results: Her- 2 protein expression was detected in 3994 cases. Her- 2 overexpression was observed in 1064 cases (26.6%), with 15.5% showing moderate overexpression and 11.1% showing dramatic overexpression. Her- 2 overexpression was observed in 26.5% of premenopausal cases and 26.8% of postmenopausal cases; it was seen in 24.3% of node- neg-ative and in 29.6% of node- positive cases. Her- 2 overexpression was positively correlated with axillary lymph node status and negatively correlated with age; it had no correlation with clinical tumor stage,histological grade, tumor size or pathologic type. For some cases with a specific clinicophathological status, Her- 2 overexpression is correlated with tumor stage and histological grade. Conclusion: Axillary lymph node status and age can be used as independent predictors for Her- 2 overexpression.