Diabetic retinopathy is a leading cause of loss of vision in the United States. Results of recent population-based studies and randomized controlled clinical trials suggest that glycemic control can lower the incidence and prevent the progression of retinopathy and loss of vision associated with diabetes. In addition, data from clinical trials showed that timely photocoagulation treatment of severe proliferative retinopathy or clinically significant macular edema prevents loss of vision. This report reviews the epidemiology of diabetic retinopathy and highlights areas in need of further epidemiologic research.