We have estimated the prevalence of diabetes and impaired glucose tolerance from the Busselton 1981 Population Survey using the 1980 World Health Organization (WHO) criteria. Standardized to the Australian non-Aboriginal population aged 25 years and over, the prevalence rates in this white community were 2.5% for known diabetes; 0.9% for newly discovered diabetes; 2.9% for impaired glucose tolerance; and 6.3% for all categories of abnormal glucose tolerance. There appears to have been a real increase in the frequency of diabetes since 1966. Using fasting serum C-peptide values and clinical criteria, 14% of all diabetic subjects were insulin-dependent. The male:female ratio for all categories of abnormal glucose tolerance was 1.4:1. Data from the United States indicate spectacularly higher rates for diabetes and impaired glucose tolerance in the white population. A national study of the prevalence of diabetes and impaired glucose tolerance in Australia is recommended. For epidemiological purposes, a single blood glucose value two hours after a 75 g oral glucose tolerance test is sufficient to categorize glucose tolerance as defined by WHO.