Objective: Behçet's disease (BD) is a chronic, inflammatory, multisystem vasculitis and the etiology is not yet fully understood. Nitric Oxide (NO) is an important molecule for the vascular system which synthesised by the Nitric Oxide Synthase (NOS) enzyme. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NOS. Therefore, we aimed to investigate levels of the ADMA and its relation with exacerbations in BD patients. Methods: The subjects enrolled in this study were recruited from 34 patients with BD and 34 healthy controls. Serum levels of ADMA, arginine and citrulline were measured by HPLC with fluorescence detection. The ESR and CRP levels analyzed by routinely used methods. Results: In contrast to information in the literature, ADMA levels were found to be decreased in BD patients when compared to control. Inversely, Arginine and Citrulline levels were significantly increased in BD patients. Increased Arginine/ADMA ratios were found in the patient group. There was an inverse relation between ADMA and CRP levels. Arginine values were also correlated CRP and Citrulline levels. Conclusion: One of the reasons of high number of BD attacks in young age may be low levels of ADMA. Our study suggests that the reduced levels of ADMA in patients group may impose a possible preventive role to ADMA through decrease of NO-mediated inflammation and exacerbations of BD with aging.