Twelve patients with proliferative diabetic retinopathy were treated with panretinal photocoagulation. EOG, ERG, and OPs were recorded before and after photocoagulation. It was found that EOG and ERG were reduced after photocoagulation. This may be explained by the fact that laser radiation is absorbed mainly in the pigment epithelium. As OPs amplitude improved after treatment, OP/ERG quotient may be said to reflect the new retinal situation and to represent a means of evaluating the course of retinopathy.