Thirty men aged 44-73 years were followed from the stage of impaired glucose tolerance-detected in the Whitehall Survey-to the diagnosis of diabetes and for a minimum of 3 years after. Eight men developed diabetic retinopathy during follow-up after diagnosis, the minimum time from diabetes diagnosis being 59 months. The only significant difference between the groups with and without retinopathy was in the time from screening to diagnosis of diabetes-mean 45.3 and 71.5 months, respectively. Of baseline variables, mean systolic and diastolic blood pressure levels were substantially higher in those who subsequently developed retinopathy, though the differences were not statistically significant (p greater than 0.05).