Scoring of the pathological changes shown by fluorescein angiography in patients with diabetic retinopathy was performed to assess the severity of retinopathy and the effectiveness of treatment. A total of 480 fluorescein angiography sessions were performed in 142 eyes of 71 patients. Eleven items of 7 signs were assessed (microaneurysms, extent of non-perfused area (NP), intraretinal microvascular abnormalities, neovascularization from the optic disc or from retinal vessels, leakage from retinal vessels and macular edema). First, the gradings for the 11 items were analysed by the quantification analysis method III and classified into 6 clusters. These 6 clusters corresponded to the grades of retinopathy. The relative severity of each grade of retinopathy was calculated by this analysis. Second, in order to determine the relative contribution of each item to the grading of retinopathy, the quantification analysis method I was used with the above 6 grades of retinopathy, which were adopted as outside criteria. The regression coefficient of the extent of NP was found to be greatest. Scores were defined as the summation of the category numbers (weights) of the main 7 items.