Objective: The aim of this study was to determine the frequency of malnutrition, obesity and overweight, calculated by body mass index (BMI), in elementary school children in the Southeast Anatolia Region of Turkey. Method: This research is a cross-sectional epidemiological study and elementary school children with aged 7-16 years were included randomly by layered random sampling method. A total of selected 20 schools and 1912 students filled the questionnaires in Diyarbakir and Mardin City Centers. A questionnaire included questions related to the educational and professional status of parents, siblings, household conditions, children's demographic characteristics and body mass indexes, body weight and heights was applied to each student. Determined BMIs were classified according to the percentile values of Center for Disease Control and Prevention (CDC-US) growth charts and International Obesity Task Force (IOTF). Results: Mean age of 1040 boys (52,3%) and 872 girls (47,7%), totally 1912 students was 10,8±2,4 years and mean BMI was 17,6±2,8 kg/m2. According to CDC classification, 7,2% of male students were categorized as "underweight", 12,3% of them as "overweight", and 3,4% of them as "obese" whereas 5,5% of them were categorized as "overweight" and 0,6% of them as "obese" according to IOTF classification. In female students, 8,4% were categorized as "underweight", 11,1% "overweight", and 3,3% as "obese" according to CDC classification whereas 5,2% were categorized as "overweight" and 1,2% "obese" according to IOTF. The prevalences were not between boys and girls (p>0.05). Conclusion: In school children in the Southeast Anatolia Region, one of the most important health problems was malnutrition; however prevalances of overweight and obesity had also nonignorable levels. © 2010 Düzce Medical Journal.