PURPOSE The purpose of this article was to evaluate the efficacy and safety of intravitreal bevacizumab (Avastin) in eyes with macular edema secondary to central retinal vein occlusion (CRVO). METHODS Forty-five consecutive eyes with macular edema secondary to CRVO were included in a prospective clinical trial. Eyes were treated with 3 initial intravitreal bevacizumab injections of 1.25 mg at monthly intervals. Retreatment was based on central retinal thickness (CRT) measured by optical coherence tomography (OCT). OCT was performed monthly; fluorescein angiography was performed every 3 months. Main outcome parameters were visual acuity (VA, using the Early Treatment of Diabetic Retinopathy Study protocol) and CRT in an 18-month follow-up period. RESULTS After 18 months of follow-up, mean VA increased from 40.9 letters at baseline to 61.9 letters (+21 letters; P<0.001) at month 18; CRT decreased from 572.3 μm at baseline to 273.2 μm at month 18 (-299.1 μm; P<0.001). Neither age, duration of CRVO, baseline VA, nor baseline CRT was correlated with the change in VA. No drug-related systemic or ocular side effects were observed following intravitreal bevacizumab treatment. CONCLUSIONS Intravitreal bevacizumab is generally well tolerated and may improve VA and decrease CRT in patients with macular edema secondary to CRVO over a period of 18 months.