The purpose of this symposium on light-coagulation is not to show the superi ority of the argon-laser-coagulation or, on the contrary, of the classical photo coagulation, but rather to see, if possible, which are the respective indications and contraindications for xenon-are-coagulation as well as for argon-laser coagulation. So, for instance, the argon-Iaser-coagulator is perhaps more appropriate to treat the lesions at and around the macula and the optic disc, but for the peripheral lesions of the retina the xenon-arc photocoagulator is surely as effective. For the conservative treatment of intraocular tumours, the xenon arc-coagula tor is beyond doubt more efficacious than the argon-Iaser-coagu lator. We were very happy to have at this symposium Professor MEYER-SCHWICKE RATH, the creator and the pioneer of light-coagulation, his coworker, Professor WESSING, and Doctor HUNTER LITTLE, one of the pioneers of the laser-therapy. We thank them very warmly for having brought to us the results of their promi nent clinical experiments. After general considerations on laser-photocoagulation, we will have a discussion on macular alterations and their treatment as well as on peripheral retinal vascular or non vascular diseases. The most important part concerns the treatment of diabetic retinopathy. Finally the prevention of complications in argon laser retinal photocoagulation will be reviewed.