The efficacy of diabetic retinal screening by a nurse trained in ophthalmoscopy and of a diabetologist was assessed by comparison with fundal photography. The study was performed in 282 subjects, 59 with known diabetes and 223 participating in a screening survey, of whom 13 had diabetes and 43 impaired glucose tolerance. The prevalence of retinopathy in the diabetic subjects was 36.8% and serious retinopathy 9.5% while in the screened subjects it was 3.5% and 0.9% respectively. The characteristics of nurse examination as a test to detect retinopathy was: sensitivity 50.0% +/- CL16.8%, specificity 99.2% +/- CL0.9%, which compared with 51.3% +/- CL15.7% and 98.7% +/- CL1.2% for the doctor. The nurse failed to detect serious retinopathy as accurately as the doctor, although new vessels were missed in 5 of 6 cases by the doctor. Screening for retinopathy requires either ophthalmoscopy by an observer trained to a higher level than is common in doctors, or non-mydriatic retinal photography.