Background. Obesity has risen considerably in the Western world and the trend is increasing in non-Western, developing countries, as well. Several school screening studies showed the relation between body mass index and hypertension. In adults, obesity is associated with an increased risk of development and progression of kidney disease. However, data at the epidemiological level are limited, both for children and adults. The aim of this study was to determine the prevalence of obesity and evaluate its association with hypertension and glomerular filtration rate (GFR) among children in Turkey.