The early 21st century has seen the development of a global epidemic of obesity in both developed and developing countries. In Australia at least one in five children and adolescents are overweight or obese, with rapid rises in prevalence apparently continuing. Similar trends are seen in other countries. Child and adolescent obesity is associated with both immediate and long-term medical and psychosocial problems, including a clustering of risk factors for the development of cardiovascular disease and diabetes. Thus, obesity poses a major health problem for the paediatric population. Major environmental and societal changes have led to a decrease in physical activity, a rise in sedentary behaviour and the consumption of high fat and high-energy foods, all in turn influencing the development of obesity. Effective management involves a multimodal approach with a developmentally aware approach, involvement of the family, a focus on healthy food choices, incorporation of physical activity and a decrease in sedentary behaviour all being important. Ultimately, however, the obesity epidemic requires a major focus on primary prevention. Australia has a national strategy for the prevention of overweight and obesity that depends upon intersectoral and intergovernmental cooperation, supported by adequate resourcing and significant community ownership.