A recent epidemiological survey of the whole adult Micronesian population of Nauru has confirmed that Nauruans, along with Pima Indians, suffer the highest rate of abnormal glucose tolerance yet recorded. To establish the morbid effects of hyperglycaemia in this population, all responders to the diabetes survey were concurrently examined for diabetic retinopathy. In diabetic subjects, the crude prevalence of retinopathy was 24%. Specific rates were determined at various levels of the following characteristics: age, 2 hour post-load plasma glucose, body mass index, duration of diabetes and systolic blood pressure. Prevalence was found to rise with increasing 2 hour plasma glucose and duration, to fall with increasing body mass index and to have a quadratic relationship with age and systolic blood pressure. The multiple logistic regression model was used to determine whether the selected characteristics were significant in increasing the risk of retinopathy. Body mass index and systolic blood pressure did not contribute significantly to this risk after controlling for age. Increasing 2 hour plasma glucose significantly increased the risk of retinopathy, and duration of disease was the strongest predictor variable. This study shows that the consequences of hyperglycaemia in this Micronesian population are comparable to those already documented in European and American Indian communities.