At the present time, photocoagulation is the treatment of choice of diabetic retinopathy. It is founded on well-defined principles. The results are better than in the non-treated cases, on the condition that the indications are well established and the techniques appropriate. Fluorescein angiography remains indispensable. The objective of the photocoagulation is the destruction of ischaemic and avascular zones by large coagulations (avascular retinal photocoagulation). Depending on the severity and the rapidity of the evolution of the retinopathy, more extensive coagulations have to be performed in non-ischaemic zones (vascular retinal photocoagulation). The association of these two techniques is the so-called panretinal photocoagulation. This step need not be taken at once, but is indicated in some well-defined cases. The newly formed vessels are not coagulated, except when they are intraretinal.