In 192 diabetic retinopathy cases, Xe light coagulation was performed. Afterwards, the eyes treated were examined half yearly for at least 4 yr. Fundus photography and fluorescein angiography were made and the visual acuity was checked. In 64 cases the comparison was made in the same patient between 1 treated and the other untreated eye. The statistical results of this study permitted an assessment of the therapeutic value of light coagulation for diabetic retinopathy.