To investigate the influence of the intensity of coagulation spots on retinal function and the clinical course after panretinal argon laser photocoagulation in diabetic retinopathy, we conducted a prospective study in 24 eyes of 12 diabetics. One eye was treated with moderate spots (average: 300 mW), the fellow eye was coagulated with intense spots (average: 600 mW). The spot size was identical in both eyes. Subjective parameters (visual acuity, perimetry), as well as objective functions (ERG, EOG) and the clinical course, were studied preoperatively and on a regular base with a follow-up of 12 months. Visual acuity and fundus findings deteriorated less often in eyes coagulated with intense spots. Visual field loss, however, was more prevalent in eyes treated with intense spots. Early treatment complications only occurred with high-energy coagulation. For this reason, high-energy spots should not be used even though they might be indicated theoretically.