The aim of this study is the evaluation of the vertebrobasilar artery system in patients with Behcet's and Neuro-Behcet's disease. For this aim; 20 adults with clinically diagnosed Behcet's disease, 20 adults with Neuro-Behcet's disease, and 19 age-and gender-matched controls were examined by magnetic resonance angiography (MRA). During MRA, diameters of left vertebral artery (LVA), right vertebral artery (RVA), basilar artery (BA), and proximal segment (P1) of posterior cerebral artery between origin and junction with the posterior communicating artery were measured. In all groups, LVA was dominant than RVA (P < 0.05). The diameters of BA and right P1 of Neuro-Behcet's disease were larger than the other groups (P < 0.05). In addition, the diameters of left P1 of Neuro-Behcet's disease were larger but not statistically significant. There is no difference between the groups in terms of gender. Behcet's disease can affect vascular structures; therefore vertebrobasilar artery system should be examined in patients with Behcet's and Neuro-Behcet's disease. (C) 2014 Wiley Periodicals, Inc.