Endothelial cell activation and/or injury is a characteristic feature of Behçet's disease (BD). The local renin-angiotensin system (RAS) in the vessel wall plays a prominent role in the endothelial control of vascular tonus and contributes to inflammatory processes. Angiotensin-converting enzyme (ACE) is the regulatory component of the RAS. In this study, we investigated the distribution of different alleles of the ACE gene in patients with BD, and the influence of the I/D polymorphism on different clinical manifestations of the disease. A cohort of 90 patients with BD were evaluated for their ACE genotype (male/female: 49/41, mean age: 36.9+/-10.6 years, min/max: 16-66 years). The mean duration of symptoms was 9.5+/-6.9 years (min/max: 1-35 years). The control population was composed of 30 healthy subjects (male/female: 15/15, mean age: 31.2+/-7.1 years, min/max: 20-45). The distribution of DD, ID and II genotypes of the ACE gene was 22 (24.5%), 56 (62.2%) and 12 (13.3%) for patients with BD, and 9 (30%), 16 (53.3%) and 5 (16.7%) for healthy controls, respectively. There was no significant difference between the groups (p>0.05). Similarly, there was no significant association between the ACE gene polymorphism and ocular, neurologic or vascular involvement of BD. The ACE gene polymorphism does not seem to play a role in the pathogenesis of BD. Moreover, possession of either the D or the I allele does not have an impact on the development of ocular, neurologic or vascular manifestations of the disease.