Four human glioblastoma cell lines (U251, UWR1, UWR2, and UWR3) were tested for the expression of the cell surface receptor for urokinase-type plasminogen activator (uPA). To our knowledge there have been no previous reports about the uPA receptors (uPARs) in glioblastoma cell lines. All four glioblastoma cell lines we tested were found to bind recombinant Pro-uPA saturably and reversibly. Scatchard analysis of radioligand binding with acid-pretreated cells showed the presence of a single population of high-affinity uPARs on glioblastoma cells. Northern blot analysis confirmed that glioblastoma cells like other human cell lines express a 1.4-kilobase uPAR mRNA and 2.4-kilobase uPA mRNA. The significance of the uPAR in the invasive potential of the cells was examined by incubating uPAR antibody in an in vitro invasion assay. The anti-uPAR monoclonal antibody blocked the invasion effectively in a Matrigel assay, in which inhibition of invasion ranged between 20 and 57% for the cells studied. These data suggest that the uPARs contribute significantly to the invasive capacity of the cells, possibly by facilitating uPA activity.