Behcet's syndrome (BS) is a chronic, multisystem disorder characterized by vasculitis. Approximately 25% of patients with Behcet's syndrome develop vascular complications, which may include superficial thrombophlebitis, deep vein and arterial thrombosis and arterial aneursym formation. The purpose of the present study was to evaluate the importance of serum nitrate (NO, nitrate) levels in the pathogenesis of vascular complications observed in Behcet's syndrome. 65 patients and 30 healthy volunteers were included in the study. The subjects were studied after an overnight fast, and blood samples were collected for glucose, ALT, AST, total cholesterol., triglyceride, high density lipoprotein (HDL), low density lipoprotein (LDL), homocysteine, folic acid, vitamin B-12 nitrate + nitrite (NO) and C-reactive Protein (CRP) levels and erythrocyte sedimantation rates (ESR). Scrum nitrate levels of patients with BS were found to be decreased when compared with the control (p<0,001).