Objective To investigate the expression of CD8 and CD28 lymphocytes in peripheral blood of patients with breast cancer before and after operation and explore its clinical significance.Method Flow cytometry was applied to test the expression of CD8,CD8+CD28+and D8+CD28-in the peripheral blood of both 40 patients with breast cancer and 25 healthy controls. Results The expression levels of CD8 in patients with breast cancer were significantly higher than those in healthy controls [(30.4±3.3)%VS. 30.4±3.3)%,P<0.05] . The expression levels of CD8+CD28+in patients with breast cancer were significantly lower than those in healthy controls [(10.4 ± 1.7)%VS. (14.3±2.6)%,P<0.05] . The expression levels of CD8+CD28-in patients with breast cancer were significantly higher than those in healthy controls [(25.1 ±2.8)% VS. (19.6 ±2.3)%, P<0.05] . After operation, the expression levels of CD8, CD8+CD28+and CD8+CD28-[(31.9 ±4.3)%, (15.4 ±2.7)%and (20.4±2.8)%, respectively] in peripheral blood of patients with breast cancer had no significant change compared with the healthy controls. The expression levels of CD8, CD8+CD28+and CD8+CD28-in peripheral blood of patients with breast cancer had significant difference between before and after operation. Conclusions After surgical operation, the immune defence and immune surveillance of cytotoxic T lymphocytes can be enhanced, immune suppression and tumor escape can be reduced. The assays of cell phenotypes CD8 and CD28 might be useful for evaluating the immunal state and prognosis of patient s with breast cancer.