Abstract: To study the effect of acetazolamide on Cystoid Macular Edema (CME) in patients with Behcet's disease, twenty three patients (46 eyes) who had chronic, but controlled uveitis associated cystoid macular edema were randomized into a double masked, cross - over trial comparing acetazolamide (250mg bid) versus placebo. Eighteen patients (36 eyes) completed the trial (11 males, 7 females). Although acetazolamide trial led to slightly better results in decreaing CME angiographically, over that of placebo (9 vs 4 eye) and improving visual acuities (8 eyes vs 5 eyes) but we concluded that a 4 week course of acetazolamide therapy has no statistically significant effect on neither visual aciuty results nor fluorescein angiographic findings of Behcet's Patients.