Abstract: Objective To approch the correlation relationship between the expression of PCNA and ER, PR in breast cancer and evaluate the sig nificance of combine detection in formulating endocrine ther apeutic regimen after breast cancer op-eration.Methods The immunohistochemical expression of PCNA,ER and PR were examined in 80 patients with breast cancer.Results(1)A mong 80 cases,the positive rate of ER,PR and PCNA wer e 65.0%,57.5%,63.75% respectively.(2) The positive rate of PCNA in group with lymphatic metastasis was significantly higher than that in group without lymphatic metastasis(P<0.01)and there was positive relationship between lymphatic metastasis and positive expression of PCNA(P<0.01).(3)The positive rate of PCN A in group without the expression of ER,PR was significantly higher than that in group with the expresson of ER,PR in breast cancer and there was negtive relationship between the expression of ER,PR in breast cancer and positive expression of PCNA(P<0.01).Conclusion The positive rate of PCNA is related with the positive or negative expression of ER,PR in breast cancer.Associating PCNA with ER,PR detection can provide the ancillary evidence to predict the prognosis and to formulate the treatment plan of endocrinetherapy after breast cancer operation.