Today, Behcet's disease is known as a multisystem disorder. Eye lesions, mouth and genital aphthous lesions, and skin lesions are accepted as major lesions. The disease also attacks the locomotor system, central nervous system, gastrointestinal system and also arteries and veins. According to available data, some 30% of the patients have vascular lesions; mostly thrombosis of the veins. Arterial thromboses have been rarely reported; and only a few number of arterial aneurysms are noted. Here we present an iliac artery aneurysm in a case of Behcet's disease.