The initial sign of diabetic retinopathy is considered to be microaneurysm, determined by ophthalmoscopy. To elucidate early vascular changes in diabetes, fluorescein angiography was performed in 272 eyes of 166 patients who had shown no evidence of diabetic retinopathy by ophthalmoscopy. Early retinal vascular changes shown by fluorescein angiography were seen in 181 eyes (66.5%) out of 272 eyes. These angiographic findings embraced dye leakage, dilatation of capillaries, filling defect of capillaries, microaneurysm-like spot dilatation and microaneurysm. Statistical analysis and follow-up studies for 1 to 5 years revealed that, with progression of the disease, the angiographic changes progressed in the following order: dye leakage, dilatation of capillaries, filling defect of capillaries, microaneurysm-like spot dilatation and microaneurysm.