Purpose: The purpose of this study was to compare the injection burden, central macular thickness (CMT), and change in best-corrected visual acuity after injecting 1.25 mg or 2.5 mg bevacizumab as needed in patients with primary macular edema secondary to central retinal vein occlusion. Methods: This is an interventional, retrospective, comparative multicenter study of 86 eyes with macular edema secondary to central retinal vein occlusion that were treated primarily with intravitreal bevacizumab (44 eyes, 1.25 mg; 42 eyes, 2.5 mg). The main outcome measures were the CMT and the change of best-corrected visual acuity at 24 months.Results: All patients completed at least 24 months of follow-up. The mean number of injections per eye were 7.2 for the 1.25-mg dose group and 8.1 for the 2.5-mg dose group (P = 0.4492). At 24 months, in the 1.25-mg dose group, the logarithm of the minimal angle of resolution best-corrected visual acuity improved from baseline 0.35 +/- 0.57 units (P < 0.0001) versus 0.27 +/- 0.68 units for the 2.5-mg dose group (P < 0.0001). These differences were not statistically significant between both dose groups. In the 1.25-mg dose group, 25 (56.8%) eyes gained >or=3 lines of Early Treatment of Diabetic Retinopathy Study visual acuity and 6 (13.6%) lost >or=3 lines of Early Treatment of Diabetic Retinopathy Study visual acuity. In the 2.5-mg dose group, 24 (57.1 %) eyes improved >or=3 lines of Early Treatment of Diabetic Retinopathy Study visual acuity and 7 (16.7%) lost >or=3 lines of Early Treatment of Diabetic Retinopathy Study visual acuity. The CMT in the 1.25-mg dose group improved from 635 +/- 324 microm to 264 +/- 160 microm (P < 0.0001) versus 528 +/- microm to 293 +/- 137 microm in the 2.5-mg dose group (P < 0.0001). There was no statistically significant difference between both dose groups with regard to the CMT reduction.Conclusion: Intravitreal bevacizumab at doses up to 2.5 mg seems to be effective in improving visual acuity and reducing CMT in macular edema secondary to central retinal vein occlusion. There were no statistically significant differences between the two dose groups with regard to the number of injections, CMT, and change in visual acuity.