Behcet’s disease is a recurrent multisystem vasculitis that can affect almost any system of the body, including mucous membranes of the mouth, urogenital system, skin, joints, vascular system, central nervous system, pulmonary and gastrointestinal systems, and the eye. Diagnosis is made on the basis of the criteria proposed by the International Study Group for Behcet’s disease in 1990. According to the criteria,recurrent oral ulceration must be present and at least two of the following : recurrent genital ulceration, eye lesions,skin lesions, or a positive pathergy test(development of a papule or pustule following a needle prick to the skin). Helical CT as a noninvasive technique is the most appropriate diagnostic method because it provides excellent vascular images with the contrast material applied in small doses over a very short time. Helical CT can be used for diagnosis and follow-up of the pulmonary aneurysm in BD.