To study the expression of P185 in breast infiltrating ductal carcinoma and its value. Methods 52 cases of breast infiltrating ducT,al carcinoma were examined for P[85 by the method of S-P immunohistocbemistry. Results 30 cases of breast infiltrating ductal carcinom (57. 7%) were positive in P185 expression. P185 over-expression was not related to histological grade,turnout size and lymph node metastasis (P> 0. 05), but in significantly negative relation to ER expression (P<0.01). Conclusion The examination of P185 and ER in couples is tee ommended and it is related to the selection of effective anticarcinogens.