Objective: To study the expression and clinical significance of urokinase-type plasminogen activator (uPA) in breast cancer. Methods: Applying streptavidin-biotin complex (SABC) immunohistochemical technique, expression of uPA was studied in 100 patients with primary breast cancer. Results: There were 55 patients with high uPA expression, and 45 with lower expression. There was significant correlation between uPA expression and TNM stage, lymph node status, and the tumor size. Neither age, menopausal status, nor ER status was significantly related with level of uPA expression. The patients with high expression of uPA had significantly shorter disease-free survival (DFS)and overall survival (OS) than did those with low expression of uPA. Univariate analysis showed that uPA as a prognostic factor was of similar magnitude to lymph node status and TNM stage, but stronger than that of ER status and tumor size. UPA was an independent prognostic factor affecting disease-free survival and overall survival. Conclusion: uPA appears to be a strong and independent biologic marker for predicting prognosis of breast cancer.