We studied the effect of macular grid photocoagulation on the retinal vessels, retina, retinal pigment epithelium, and choroid of normal cynomolgus monkeys. Argon blue-green laser photocoagulation, similar to that employed for treating macular edema due to branch retinal vein occlusion, resulted in a decreased retinal capillary area at both one and five months after treatment. The photoreceptors and retinal pigment epithelium between laser lesions were altered at three days after treatment, but their appearance returned to normal by five months. The significance of these findings is discussed with regard to resolution of macular edema and improvement in vision following grid photocoagulation.