The overexpression of C-erb B-2 oncogene in breast cancer was examined in 245 cases with immunohistochemical techniques.The results showed that:①Significant associations of C-erb B-2 overexpression with high histological grade (Ｐ＜0.05), positive axillary node status (Ｐ＜0.05)， advanced clinical stage (Ｐ＜0.05) and the absence of hormone receptor(Ｐ＜0.05) were identified in breast cancer.②Overexpression of C-erb B-2 oncogene was related with 5-year and 10-year survival rate, and considered as a prognostic factor for breast cancer independent of axillary node status. Detection of C-erb B-2 oncogene overexpression could be arranged as a regular pathological examination in breast cancer.Combined with axillary node and estrogen receptor, progestin receptor status, the results can be used in determining the prognosis and planing the treatment programme in breast cancer.