An analysis by fluorescein angiography of the first signs of retinopathy in 161 diabetic children showed that microaneurysm-like spot dilatations, microaneurysms, focal capillary dilatations, leakage, generalized capillary dilatations, retinal hemorrhages, areas of capillary non-perfusion and capillary remodelling, in decreasing order of frequency, were features of the onset of retinopathy. However, microaneurysm-like spot dilatations and both focal and generalized capillary dilatations were considered to be too subjective for use in further quantitative analysis. Retinopathy was not found in children less than 12 years of age and was detected only after at least 3 years of diabetes. The mean duration of diabetes before the occurrence of the first lesions in 118 affected eyes was 8.2 years. The mean age at which lesions occurred was 16.4 years. Although capillary non-perfusion was rarely an initial lesion, occurring after a longer duration of diabetes and at a later age than the other lesions, no significant difference could be found between the various types of lesions for either the patient's age at their onset or the duration of diabetes. The type of initial lesion was also unrelated to sex, age at the onset of diabetes, or metabolic control.