Behcet's disease is a chronic, inflammatory disorder of unknown cause, characterized byrecurrent oral, genital ulcers, and uveitis. Although its etiology remains uncertain,Endothelial activation is one of the possiple mechanism of pathogensis of Behcet'sdisease which is attributed to to vascular affection and can be assessed by measuringflow mediated dilatation . The recurrent study included 30 patients and 15 subjects as acontrol group who were undergone measuring flow mediated dilatation of the brachialartery in response to sheer stress and that induced by sublingual nitrate application byusing Doppler ultrasonography for evaluation of endothelial dysfunction.