Behcet's disease (BD) commonly presents with articular manifestations and thrombotic vasculopathy. Arthritis of BD characteristically demonstrates a recurrent and nondestructive course. The pathobiological basis of the thrombotic vasculopathy and protective factors against cartilage destruction in arthritis of BD have not been elucidated. Apart from being involved in fibrinolysis and thrombolysis, the plasminogen activation system can contribute to the pathogenesis of destructive joint diseases such as rheumatoid arthritis (RA). Plasminogen activator inhibitor-1 (PAI-1) is a well known fibrinolysis inhibitor. In this study, local synovial fluid and circulating plasma PAI-1 concentrations of BD were assessed in comparison to RA patients and healthy controls to investigate the nonerosive, nondestructive nature of Behcet arthritis. Twelve patients with BD (mean age 34+/-11 years, males:females 6:6), 15 with RA (mean age 36+/-8 years, males:females 3:12), and 15 healthy adults (mean age 32+/-10 years, males:females 6:9) were included in this study. Plasma PAI-1 antigen levels and PAI-1 activities were significantly greater in BD patients than in RA patients and healthy controls (P<0.001). Synovial fluid levels of both parameters were also higher than in RA patients (P<0.001). These results suggest that PAI-1 may promote hypofibrinolysis of Behcet's vasculopathy and also have a protective role in the arthritis of BD.