The incidence of blindness due to diabetic retinopathy has increased from less than 1 % in 1930 to more than 15% in 1960. A similar increase has occurred in the incidence of other forms of diabetic degenerative vascular disease. Clinical statistics have demonstrated that the incidence of retinopathy is directly related to the duration of the disease and that the onset of retinopathy can be delayed and its severity limited by careful diabetic control. Despite a major research effort the pathogenesis of diabetic retinopathy is not clear and there is no specific treatment. Early case finding and strict control are the only methods now available for the prevention and modification of the degenerative vascular complications of diabetes.