Large VESSEL involvement is one of the hallmarks of Behcet’s disease (BD) but its prevalence varies widely due to ethnic variation or environmental factors. The aim of this study is to find the characteristics of vasculo-Behcet (VB) in Iran. In a cohort of 4769 patients with BD, those with vascular involvement were selected. Different manifestations of disease were compared with the remaining group of patients. A confidence interval at 95% (CI) was calculated for each item. Vascular involvement was seen in 409 cases (8.6%; CI, 0.8). Venous involvement was seen in 396 cases, deep vein thrombosis in 294 (6.2%; CI, 0.7), superficial phlebitis in 108 (2.3%; CI, 0.4) and large vein thrombosis in 45 (0.9%; CI, 0.3). Arterial involvement was seen in 28 patients (25 aneurysms and 4 thromboses). Thirteen patients showed both arterial and venous involvement. The mean age of the patients with VB was slightly higher (P<0.03), but the disease duration was significantly longer (P<0.0003). VB was more common in men. As the presenting sign, ocular lesions were less frequent in VB (P<0.0006), while skin lesions were over 2 times more common in these cases (P<0.000001). VB was associated with a higher frequency of genital aphthosis, skin involvement, joint manifestations, epididymitis, CNS lesions and GI involvement. The juvenile form was less common in VB (P<0.03). High ESR was more frequent in VB (P=0.000002), but the frequency of false positive VDRL, pathergy phenomenon, HLA-B5 or HLA-B27 showed no significant difference between the two groups. 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 disease duration