The objective of the Australian Diabetes and Lifestyle Study (AusDiab) was to determine the frequency of diabetes and other categories of glucose intolerance (impaired glucose tolerance (IGT) and impaired fasting glucose (IFG)), as well as other cardiovascular risk factors in Australia and to compare the prevalence with previous Australian data. The study involved a national sample involving 11 247 participants aged 25 years from the six states and the Northern Territory. They were examined in a cross-sectional survey using the 75-g oral glucose tolerance test to assess fasting and 2-h plasma glucose levels. The World Health Organization diagnostic criteria were used to determine the prevalence of abnormal glucose tolerance. The prevalence of diabetes in Australia was 8.0% in men and 6.8% in women, and an additional 17.4% of men and 15.4% of women had IGT or IFG. The overall diabetes prevalence in Australia was 7.4%, and an additional 16.4% had IGT or IFG. Diabetes prevalence has more than doubled since 1981, and this is only partially explained by changes in age profile and obesity. Almost one in four Australians 25 years and over has either diabetes or a condition of impaired glucose metabolism. This condition is associated with substantially increased immediate risk of heart disease as well as increased risk of diabetes in the future. In addition, there were high prevalences of other key cardiovascular disease risk factors. Australia has a rapidly rising prevalence of diabetes and other categories of abnormal glucose tolerance. The prevalence of abnormal glucose tolerance in Australia is one of the highest yet reported from a developed nation with a predominantly European background.