Abstract: Behcet's Disease (BD) has been found to be related to the first class HLA antigens, the B5. In Iran, B5 is present in 64% of BD patients versus 34% in normal population. The relative risk is 3.33. Uveitis has been demonstrated to be related to the presence of B5. in our study the posterior uveitis was present in 59% of patients with B5 versus 48% without it (p<0.02). Retinitis was also more frequent in patients with B5 (47% versus 36%, p<0.02). The same phenomenon was also observed with genital ulcerations (74% versus 65%, p<0.05), Joint manifestations (70% versus 61%, p<0.05), and in patients with the complete form of the disease (48% versus 38%, p<0.02). When males and females were studied separately, the influence of B5 appeared to be sex related. In males, ophthalmologic and Joint manifestations, and the complete form of the disease, were seen more frequently in the B5 group. While in females, genital ulcerations were seen more frequently in the presence of B5. Complete data will be discussed.