Changes of the retinopathy score with the progression of diabetic retinopathy were investigated in 87 eyes of 44 diabetic patients. The previously reported retinopathy scoring system of Yamashita et al., utilizing fluorescein angiography, was used. Factors relevant to an increase of the retinopathy score were determined using quantification analysis (a type of multivariate analysis). The factors assessed were microaneurysms, the extent of retinal nonperfusion, intraretinal microvascular abnormalities, the grade of fluorescein dye leakage from retinal vessels, neovascularization, the grade of macular edema, the HbA1c level and the duration of retinopathy. The retinopathy score increased in 50 eyes (57%) after a mean follow-up period of 24.9 months. The probability of the score increasing in the eyes with advanced background retinopathy was 78%. The probability in eyes with preproliferative or proliferative diabetic retinopathy was 52% or 11%, respectively. The mean increase of the score in one year was 3.0 for all subjects. The increase in the eyes with advanced background, preproliferative or proliferative diabetic retinopathy was 6.1, 2.8 or 0.1, respectively. Our results suggest that this scoring system can effectively detect changes of background and preproliferative retinopathy. According to quantification analysis, the factor most relevant to the increase of the score was retinal nonperfusion. Dye leakage and neovascularization were also relevant, in descending order.