A follow-up study on 67 diabetic patients with new proliferation on the nerve head (neovascularisation of the disc and fibrous proliferation of the disc) was carried out for 4 years. The patients were randomly assigned for treatment with argon laser and xenon photocoagulation in only one eye, with the other eye serving as a control. The disc condition was periodically evaluated for NVD, FPD, and for the relations between them according to a grading taxonomy which was previously established. It was found that there were significant differences in NVD and FPD evolution between treated and untreated eyes. The various parameters concerned with these differences were observed, analysed, and correlated.