Aims. To establish the prevalence of child overweight and obesity in the USA using IOTF-recommended definitions. Methods. Original data from the NHANES surveys for 1999–2000 and 2003–2004 were analysed using the IOTF cut-offs and prevalence levels calculated using sample weightings provided. Results. In 1999–2000, overweight (including obesity) was affecting 29% of school-age children. By 2003–2004 this figure had risen above 35%. Obesity alone was affecting 10% of school children in the 1999–2000, and over 13% in 2003–2004. Conclusion. The United States is experiencing levels of child overweight and obesity that are among the highest recorded in any country in the world.