The initial disorder leading to any kind of diabetic retinopathy is hypoxia. After exhaustion of the compensatory autoregulation (vasodilatation and increase of the volume flow), the blood-retina barrier breaks down, and parts of the central retinal capillary network fall out (pre-retinopathy). In the non-proliferative and pre-proliferative stage, either disturbance of permeability or occlusion of capillaries is the prevailing process. The stage and predominance of one of the two pathogenic factors, which eventually may be jointed by vascular proliferation, are decisive for the application of light coagulation. The plan of the procedure must be based upon fluorescence angiography. If all progressive changes are treated, and fluorescence angiographic controls are made in intervals of several weeks or months, according to the stage and form (primary exsudative or primary occlusive) of the retinopathy, this procedure is preferable to the coagulation of big retinal areas (retinal ablation), and a maximum of retina with normal vascularisation can be saved. Medical treatment comprising calcium phosphate, the vasoprotecting Doxium, and clofibrate as a depressor of the lipid level in the blood, play a secondary role. Finally, hypophysectomy could not maintain its place in modern treatment of diabetic retinopathy.