Abstract: Objective :To investigate the expression of AgNOR in peripheral blood T lymphocyte of breast cancer, and their correlation with clinical pathological significance. Methods :The expression of AgNOR in peripheral blood T lymphocyte in 80 patients with breast Cancer, 40 patients with breast fibroadenoma, 25 Patents with mastitis and 75 patents with healthy controls by the KL imaging system(the ratio of silver stained nucleolus area and nucleolus area of T lymphocyte, LS%), and their correlation with clinical pathological factors was explored. At the same time, CA153 and carcinoembryonic antigen (CEA) were measured by bio- antibody sandwich. Results: The expression of AgNOR in periph- Results :eral blood T lymphocyte in patients with breast cancer (5.88 ).OS%was much lower than that of the healthy control group (7.07 x.81%), breast fibroadenoma (6.58 x.72%) and mastitis (9.58 x.68%)(P= 0.000). The expression of AgNOR in patients with mastitis was much higher compared to the healthycontrol group, breast fibroadenoma and breast Cancer (P=0.000); There was no statistical difference betwen the subjects with healthy control group and breast fibroadenoma(P>0.05). The positive rate of AgNOR (65.00%) was much higher than that CA153 (17.50%)and CEA (12.50%)in patients with breast Cancer (P=0.000). The expression of AgNOR was positively correlated with tumor stages (P<0.05), but was not related to age, tumor size, lymph node status (P>0.05). Conclusions :The expression of AgNOR is a objective biological parameter to estimate the development and progression of breast cancer. In addition, the results demonstrated that the analysis of AgNOR might play an important role in the diagnosis, differenciation and clinical monitoring or cancers.