Cancer cell invasion is accomplished by the concerted action of several extracellular proteolytic enzyme systems, one of which is the urokinase plasminogen activation system. The different components of this system. e.g. urokinase plasminogen activator (uPA), its receptor uPAR, as well as its main inhibitor plasminogen activator inhibitor type 1 (PAI-1) have all been shown to have prognostic value in breast cancer, i.e. high tumor levels are associated with a poor prognosis. In order to further substantiate the prognostic value of uPA and PAI-1, we have tested the cutpoints (median values and optimized outpoints) from our first study (Cancer Res 53: 2513-2521, 1993) in an independent group of breast cancer patients. Breast cancer cytosols from 100 premenopausal and 150 post-menopausal node positive patients were included. The median observation time was 80 months (range 49-145). Univariate analysis showed that high PAI-1 levels (above the median PAI-1 value) were significantly associated with short recurrence-free survival (RR: 1.65; 95% CI: 1.04-2.63; P = 0.03) and short overall survival (RR: 2.46; 95% CI: 1.52-3.96; P = 0.0001) in postmenopausal patients. Postmenopausal patients with high uPA levels (above the median uPA value) had a significantly shorter recurrence-free survival (RR: 2.04; 95% CI: 1.17-3.56; P = 0.01) and overall survival (RR: 2.07; 95% CI: 1.16-3.70; P = 0.01) than patients with low uPA values. Nearly identical results were obtained when using the optimized PAI-1 or uPA value. In a Cox multivariate analysis which included other established prognostic factors, high PAI-1 was found to be an independent prognostic variable predicting short overall survival with a relative risk of 2.27 in postmenopausal women, and high uPA was found to be an independent prognostic variable predicting short recurrence-free survival with a relative risk of 1.86 in postmenopausal women. The present study indicates that uPA and PAI-1 are independent and significant prognostic variables in subsets of breast cancer patients.