Abstract: Objective To investigate the prognostic value and clinicopathological characteristics of tumor infiltrating CD8+ lymphocytes in operable breast cancer. Methods Paraffin sections were retrospectively collected from 681 cases of operable breast cancer patients from January 2000 to December 2008 in Cancer Center of Sun Yat’sen Unversity. Immunohistochemical staining of tissue microarray were used to assess the density of tumor infiltrating CD8+ lymphocytes. The number of CD8+ lymphocytes counted in tumor stroma，and the relationship with clinical outcome and clinicopathological characteristics was determined. Results The proportion of high infiltrating CD8+ lymphocytes was 42.0%（286/681） in interstitial tissues of breast cancer. The infiltrating CD8+ lymphocytes were related to age at diagnosis， menstruation， tumor size， lymph node metastasis， pathological stage, lymphovascular invasion， histological grade， hormone receptor status and HER-2 status（P＜0.05）. The 5year disease-free survival rate and 5-year overall survival rate in the whole patients were 79.2% and 87.6%， respectively. The 5-year disease-free survival rate of patients with high and low tumor infiltrating CD8+ lymphocytes were 83.2% and 68.8%，the 5-year overall survival rate were 89.5% and 82.2%. The high tumor-infiltrating CD8+ lymphocytes were associated with better survival（P＜0.05）. In multivariate analysis， the number of CD8+ lymphocytes was an independent prognostic factor influencing disease-free survival and overall survival. Conclusion Infiltrating CD8+ lymphocytes may become a prognositic predictor for operable breast cancer.