Abstract: Objective: To compare the expression of HER-2/neu/c-erbB-2 oncogene detected by chromogenic in situ hybridization(CISH) and immunohistochemistry(IHC) in breast cancer. Methods: The formalin-fixed paraffin-embedded breast cancer samples(44 cases) were selected and these samples were detected by IHC.Among them,there were 9 cases with negative expression,9 cases with score(+),13 cases with score(++),13 cases with score(+++).Twenty-two cases with HER-2 IHC positively expressed were examined retrospectively(including 9 cases with score(+) and 13 cases with score(+++).Results: In the nine cases with score(+) by IHC,all cases were negatively expressed with CISH.Two of the 13 cases with score(+++) showed CISH-negative(15.38%),1 cases failed to show amplification,the remaining 10 cases showed gene amplification,thus the concordant ratio between IHC and CISH was 76.92%.Certain concordance to the examination of HER-2 status(P=0.001) was found in the two kinds of methods.The results of gene amplification detected by IHC and CISH had no concordance with types of breast cancer(P<0.05).Conclusions: The results of gene amplification detected by CISH have high concordance with IHC.IHC is a choice in primary screening for HER-2 expression status.The concordant ratio between IHC and CISH is high,CISH is more accurate than IHC.Patients with proven amplification of HER-2/neu may benefit from treatment with anti-HER-2 monoclonal antibodies.