- Effective surveillance of trends in paediatric overweight and obesity requires the establishment of valid cutoff values to identify children at risk. In Israel, standard values for childhood BMI-for-age are currently based on growth charts published by the US Centers for Disease Control and Prevention. However, the appropriateness of using US reference values in populations outside the US is questionable, due to inherent differences in ethnicity, culture and socioeconomic status. We recorded data from 9,988 children aged 6–12 selected by random cluster sampling within the framework of school-based health surveys conducted in Israel during the years 1997 and 2000. We constructed population-specific centile BMI-for-age curves valid for Israeli children, and compared these curves to current standard US and international reference values. Curves were constructed using LMS statistical curve smoothing methods. The data set of Israeli schoolchildren produced reference centiles substantially different than those based on US children. Israeli reference values were closer to centile curves published by the International Obesity Task Force. In conclusion, local and national health planners should recognize the intrinsic limitations associated with the use of “standard” reference values in defining paediatric overweight and obesity in dissimilar populations. The results of this large population-based study highlight the need for population-specific BMI-for-age reference values, in order to accurately describe the prevalence of paediatric overweight and obesity.