Behcet's disease (BD) is a multisystemic disorder characterised by recurrent oral and genital ulcers. Vasculitis and thrombotic events are the most important causes of mortality. Thrombosis is the major clinical finding in patients with BD, but the cause of the thrombosis is still unclear. Thromboelastography is an alternative method to evaluate almost all steps of the hemostatic system. Today, the modified rotation thromboelastogram (ROTEM) is a newer coagulation test and a more powerful technique. Our aim in this study was to investigate whether hemostatic mechanisms play a role in the development of thrombosis in BD patients by using ROTEM. Thirty BD patients, 20 ankylosing spondylitis patients, and 14 healthy controls who are not taking anti-aggregant or anti-coagulant therapy were included in the study. Whole blood count, protrombin time, activated protrombin time, fibrinogen, D-dimer levels, and ROTEM parameters (clotting time, clot formation time (CFT), and maximum clot formation(MCF)) were determined by INTEM and EXTEM analysis. Of the 30 patients with BD, 19 were women and 11 were men, and mean age was 40.6 ± 11.2. Two of the BD patients had vascular involvement, but none of them were in active phase of the disease during the study. In INTEM assay, MCF (p < 0,001) value was significantly increased, and CFT (p>0.05) value was decreased in BD patients compared with the control group. In the EXTEM assay, there was a similar significant increase in MCF (p=0.002) value and a decrease in CFT (p=0.002) value in BD patients compared with the control group. The results of our study indicated that primary hemostatic mechanisms which can be detected by ROTEM may play a role in the development of thrombosis in patients with BD. © 2013 Clinical Rheumatology.