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