The WESDR has provided precise estimates of the prevalence, and 4-year incidence and progression of diabetic retinopathy. It has provided evidence of a possible causal relationship between specific risk factors, such as hyperglycemia and the development and progression of retinopathy. Our data support current recommendations for ophthalmologic examinations for people with diabetes. In 1990 we will reexamine the cohort to determine the 10-year incidence and progression of diabetic retinopathy, macular edema, and visual impairment.