Objectives: To determine the population prevalence of overweight and obesity among Australian children and adolescents, based on measured body mass index (BMI). To determine if overweight and obesity are distributed differentially across the population of young Australians.

Methods: Data from three independent surveys were analysed. In each, height and weight were measured by trained surveyors using valid, comparable methods. BMI (kg/m2) was used as the index of adiposity and recently published international BMI cutoff values used to categorise each subject as non-overweight, overweight or obese.

Results: The population prevalence and distribution of overweight, obesity and overweight/obesity combined were generally consistent across datasets. The ranges of the prevalence of non-overweight, overweight, obesity and overweight/obesity combined were 79–81%, 14–16%, 5% and 19–21% (boys) respectively and 76–79%, 16–18%, 5–6% and 21–24% (girls). There were no consistent relationships between the prevalence of overweight/obesity and sex, age or SES. Their prevalence was up to 4% higher in urban than rural areas among boys, but there were no differences between urban and rural girls. The data suggest a higher prevalence of overweight/obesity among students from European or Middle-Eastern cultural backgrounds.

Conclusions: Some 19–23% of Australian children and adolescents are either overweight or obese. Although urban/rural, SES and cultural background differentials were noted, only the last warrants a targeted health promotion response.

Implications: Overweight/obesity is a prevalent health risk factor among Australian children and adolescents. More information is needed to understand whether targeted approaches are required for specific ethnic groups in addition to broad, population-based approaches.