Abstract: Objective To study the relation between expression of IL-2 in breast cancer tissue and clinicopathological characteristics and prognosis of breast cancer. Methods Clinical data about 130 patients with stages Ⅰ-Ⅲ breast cancer admitted to our hospital from January 2000 to December 2002 were retrospectively analyzed and their paraffn sections were collected. Relation between expression of IL-2 detected with immunohistochemical staining and clinicopathological features and prognosis of breast cancer was analyzed. Results The IL-2 was mainly expressed in mesenchymal lymphocytes of breast cancer. The IL-2 expression levels of disease-free survival (DFS) and distant disease-free survival (DDFS) were signifcantly higher in high density IL-2 mesenchymal cells than in low density IL-2 mesenchymal cells (P＜ 0.05). The overall survival (OS, HR=0.301, P=0.059), DFS(HR=0.156, P=0.012)and DDFS(HR=0.171, P=0.018)were the independent predicting factors for high density IL-2 mesenchymal cells. Conclusion Expression of IL-2 in breast cancer tissue can predict the prognosis of breast cancer. Relapse and metastasis of breast cancer are related with the high death rate in breast cancer patients with a low IL-2 expression level.