Abstract: lntroduction: Ocular lesions of Behcet's Disease (BD) need aggressive treatment to prevent from severe loss of vision or blindness. Cytotoxic drugs are necessary for the treatment. A short-term study with azathioprine (AZA) was presented to the 8th lnternational Conference on Behcet's Disease. The aim of this study is to present the results for a longer period of time. Materials & methods: Patients (32) who received more than 9 months of treatment were selected for this study. They received 2-mg/kg azathioprine daily. They also received 0.5-mg/kg/daily of prednisolone. Upon the control of inflammation prednisolone was gradually tapered. A Disease Activity Index (DAI) was calculated for anterior uveitis (AU), posterior uveitis (PU), and retinal vasculitis (RV). Visual acuity (VA) was calculated with a Snellen chart. A Total Adjusted Disease Activity Index (TADAI) was calculated for each patient on the sum of the indexes of both eyes. A confidence interval (C!) was calculated for each percentage. Results before and after the treatment were compared by the Student paired t test with Yates correction. Results: The mean follow up time was 19.5 months (maximum 32 months). The entry data were as follow. The mean DAI were 2.8 for AU, 2.0 for PU, and 2.6 for RV. The mean VA was 4.7, and the mean TADAI was 33.7. After the treatment the mean DAI for AU improved to 0.8 (p< 0.007), for PU to 0.6 (p<0.0001), and for RV to 1.9 (p=0.086, not significant), The mean VA improved to 6.2 (p< 0.0003), and the mean TADAI to 20 (p<0.0001 ). AU improved in 80% (CI = 14.9), PU in 86% (CI = 11.4), RV in 65% (CI = 15.9), and VA in 69% (CI = 13) of the eyes. TADAI improved in 84% (CI = 13.1) of patients. Discussion: For comparison, patients under PCP (193) who had more between 9 and 33 months of treatment (as for azathioprine group) were selected. The mean follow up was 18 months. The mean DAI were 2.2 for AU, 2.3 for PU, and 2.2 for RV. The mean VA was 3.4, and the mean TADAI was 40.3. After the treatment the mean DAI for AU improved to 0.8 (p< 0.0001), for PU to 1.1 (p<0.0001), and for RV to 1.2 (p=0.0001). The mean VA improved to 3.8 (p= 0.01), and the mean TADAI to 29.4 (p<0.0001). Conclusion: These results confirm the preliminary results mentioned above. Azathioprine is not enough efficient in patients with RV. It is best indicated for PU.