BACKGROUND In previous studies, higher expression of PREX1 (PtdIns (3,4,5)P3-dependent Rac exchanger 1) has been detected in some subsets of breast cancer, and activation of PREX1 has been associated with tumor progression in vivo. However, an association between PREX1 and breast cancer prognosis has not been examined. MATERIAL AND METHODS In this study, we investigated the expression and correlation of PREX1 with important clinical factors and prognosis of patients with breast cancer. Immunohistochemical staining was performed for 121 tumor tissue specimens obtained from primary breast cancer lesions. RESULTS We found that 55 tissues exhibited positive staining for PREX1. Moreover, tumors positive for PREX1 were found to have significant association with recurrence rate (P=0.000) and metastasis rate (P=0.001). Univariate and multivariate regression analyses also identified PREX1 expression as an independent variable of disease-free survival. Our analyses indicate that high levels of PREX1 expression were related to longer disease-free survival in patients with breast cancer (P=0.013). CONCLUSIONS PREX1 is a favorable variable of prognosis for breast cancer patients, these study results need to be confirmed in larger research studies.