In this study of branch retinal vein occlusion, we distinguished between cystoid macular edema caused by increased capillary pressure and noncystoid edema due to hard exudates in the macula caused by chronic leakage from vascular abnormalities in the posterior pole or midperiphery. We performed laser photocoagulation in 51 eyes with cystoid macular edema to achieve focal narrowing of the retinal arterioles perfusing the macular area affected by the cystoid edema; good anatomic and functional results were achieved in 40 of these eyes (78%). In 25 of the five eyes, the treated segment of the retinal arteriole was outside the area of macular edema; results were successful in 19 of these eyes (76%). In 14 eyes with noncystoid exudative macular edema, we performed laser photocoagulation to the vascular abnormalities; good anatomic and functional results were obtained in 12 of these (86%).