A diabetes prevalence study in 1975 on an isolated urbanized Central Pacific island (Nauru) showed rates comparable to the American Pima Indians--the highest yet recorded in the world literature. This paper reports the results of a follow-up study and the high prevalence has been confirmed. In this survey of 417 people aged ten years and over, 9.8% were known diabetics. With a plasma glucose of 160 mg/100 ml or over at two hours after a 75 gram oral glucose load as the criterion of diagnosis, , diabetes was detected in a further 19.2%, making a total diabetic population of 29% in the population studied. The prevalence of diabetes was 44% in people aged 20 years and over. A further 7% had borderline diabetes on the basis of a two-hour plasma glucose of 140--159 mg/100 ml. Parity did not appear to be a causative factor in relation to the high diabetes prevalence. However, obesity is common in this community and is more marked than that seen in other Pacific or Caucasian communities. The high prevalence of diabetes in this population appears to be related to the inter-action of environmental factors, such as obesity, with a diabetic genotype. The results confirm the possible detrimental effects of westernization on native populations.