The prevalence of type 2 diabetes in Australia has doubled over the past 20 years; more than 7% of Australian adults now have diabetes. An additional 16% of Australian adults have lesser abnormalities of glucose tolerance. Insulin resistance and increased cardiovascular risk occur in both these groups (the metabolic syndrome). 50% of cases of type 2 diabetes are undiagnosed; screening is indicated in everyone aged over 55 and in younger people with risk factors such as obesity, hypertension, family history or certain ethnic backgrounds. Dietary modification and increased physical activity have been shown to dramatically reduce the incidence of type 2 diabetes in those at high risk. General practitioners should target individuals at high risk, but this needs to be reinforced by community-wide preventive action. National prevention programs are needed, but GPs can contribute through screening and lifestyle advice.