The plasminogen activation system plays a crucial role during cancer invasion and metastasis. In the solid tumor, urokinase-type plasminogen activator (uPA), plasminogen activator inhibitor type-1 (PAI-1) and uPA receptor (uPAR) are considered as prognostic factors. In this study, we have investigated whether secretion of the uPA, PAI-1 and uPAR from the primary breast cancer tissue can be detected in the blood of the patients using the ELISA assay. We have found that the plasminogen activation system (uPA, PAI-1, uPAR) of tumor tissue is activated from the early stage of breast cancer. However, only a number of metastatic lymph nodes was a prognostic factor in multivariate analysis for relapse. The blood level of the plasminogen activation system correlated with that of tissue in an order of uPAR (r(2)=0.61; P=0.001), uPA (r(2)=0.35; P=0.001) and PAI-1 (r(2)=0.11; P=0.001). We conclude that the total uPAR level of cancer tissue can be substituted by that which is detected in the blood for further clinical applications.