Abstract: Introduction: Vascular involvement, as a hallmark of Behcet’s disease (BD), involves arteries and veins of all size and may be a poor prognostic sign. Like the other manifestations of the disease, its prevalence varies widely according to the reports from different parts of the world (7.7 to 60%). The difference may be due to ethic variation or environmental factors. The aim of this study is to find the characteristics of vascular Behcet (VB) in Iran. Materials & Methods: In a cohort of 3723 patients with BD, those with vascular involvement were selected. Different manifestations of the disease, including 100 clinical and paraclinical parameters, were determined and compared with the remaining group of patients (not having VB) by chi square test and Fisher exact test. A confidence interval at 95% (CI) was calculated for each item. Results: Vascular involvement was seen in 323 cases (8.7%, CI=0.9). Venous involvement was seen more frequently: Deep vein thrombosis in 230 (6.2%, CI=0.8), superficial phlebitis in 86 (2.3%, CI=0.5) and large vein thrombosis in 36 (1%, CI=03). Arterial involvement was seen in 14 patients (12 aneurysms, 1 thrombosis and 3 with pulse weakness). Seven patients showed both arterial and venous involvement. In VB group the mean age was slightly higher (27±9.1 vs. 26±9.7 years, p=0.08), but the disease duration was significantly longer (9.3±6.7 vs. 8.4 ±6.7 years, p<0.03). VB was more common in men (78%±4.5 vs. 51%±1.7, p<0.000001). VB was associated with a higher frequency of genital aphthosis (74%±4.8 vs. 63%±1.6, p<0.00008), skin involvement (90%±3.3 vs. 72%±1.5, p<0.000001), joint manifestations (61%±5.3 vs. 36%±1.6, p<0.000001), epididymitis, (22%±5.1 vs. 10%±1.4, p<0.000001), CNS lesions (6.2%±2.6 vs. 2.7%±0.5, p<0.0005) and G.I. involvement (12%±3.5 vs. 8%±0.9 p<0.02) High ESR was more frequent in VB (75%±4.9 vs. 54%±1.7, P<0.000001), but the frequency of false positive VDRL, pathergy phenomenon, HLAB5 or HLAB27 showed no significant difference between the two groups. Conclusion: In Iranian patients with BD, vascular involvement is not common and large vessel involvement is rare. It may be sex related, and is more common in well-established disease, with multiple organ involvement and longer duration of the disease, No relationship seems to exist between vascular involvement and false positive VDRL, pathergy phenomenon and HLAB5 in BD.