Two BMI reference curves-the World Health Organization (WHO 2006) and the Centers for Disease Control and Prevention (CDC 2000)-have been widely applied to calculate the anthropometric indicators of growth (6,7). WHO (2006) was developed using children's data from 6 countries [Brazil, Ghana, India, Norway, Oman and United States of America (USA)], while CDC (2000) criteria are based on US children and adolescents aged 0-20 years. Some studies in different countries have found differences between their own child growth charts and these 2 international reference curves (8-10). Therefore, for BMI to be applicable in practice in the paediatric age group, standards should better be defined by age and gender based on local data (11,12). Now, many countries have their own BMI curves according to their child population; however, limited national data exist for Asian children, notably from children in Middle Eastern countries (12-16). This study aimed to produce BMI-forage curves for northern Iranian children aged 7-11 years and compare them with the WHO and CDC reference curves. Methods Study setting Mazandaran province is located in the north of the Islamic Republic of Iran between the Caspian Sea and Alborz mountains. It consists of 15 counties. The total population of the province in 2011 was estimated to be 3.074 million. Babol county is the biggest county of Mazandaran and is located in the middle of the province. Babol city is the third largest city in the north of the Islamic Republic of Iran. At the 2012 census, the population of Babol county was 495 472, in 149 363 families. Study design and population This was a cross-sectional survey conducted in 2012. A