Abstract: A cross sectional study was conducted to investigate the relationship between body mass index (BMI) and demographic and environmental factors among public high school students in Pattani Province. The results show that BMI is related to age group, sex, religion group, birthplace and parents` income. The prevalences of overweight and obesity of non-Muslim students are 8.7% and 3.0%, respectively. For Muslim students, these prevalences are 4.3% and 1.0%, respectively. The process of development childhood obesity could vary in populations with different cultural backgrounds. Therefore, it would be useful to examine the cultural factors influencing the development of childhood obesity.