Plasminogen activators and their inhibitor in bone tumors and tumor-like damages. Expression of urokinase- and tissue-type plasminogen activators and their inhibitor PAI-1 in the cytosolic fraction of 20 osteosarcomas, 20 chondrosarcomas, 13 giant-cell bone tumors, 5 Ewing's sarcomas, and 7 osteochondral exostoses was studied by enzyme immunoassay. The content of urokinase-type plasminogen activator increased, while the concentration of tissue-type plasminogen activator decreased in bone tumors of various histological compositions compared to osteochondral exostoses. A positive correlation was found between PAI-1 content and the volume of osteo- and chondrosarcomas. Expression of urokinase-type plasminogen activator increased in patients with primary osteosarcomas characterized by early generalization of the pathological process.