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.