Suppression of the fibrinolytic system is a well-known phenomenon in patients with Behcet's disease regardless of whether they present thrombotic complications. This finding has been related to impaired production and/or release of plasminogen activators from the vascular endothelium. In previous studies a diminished release of PF4 upon heparin stimuli was observed in plasma from patients with Behcet's disease and interpreted as an additional indicator for endothelial cell dysfunction. In the present investigations, 12 patients and 10 healthy volunteers received DDAVP infusions and euglobulin clot lysis time, factor VIII activities and 6-keto-PGF1 alpha levels in plasma were repeatedly determined before and after infusions. At different times following DDAVP infusion, euglobulin clot lysis time was significantly longer and levels of F.VIII R:Ag were lower in patients than in normals. F. VIII:C activity increased in both groups, whereas no changes were seen in the plasma levels of 6-Keto-PGF1 alpha either in normals or in patients. It is concluded that the disseminated damage of endothelial tissue associated with Behçet's disease correlates with multiple endothelial cell dysfunctions and subsequent hemostatic abnormalities.