Using stratified sampling technique 2696 adolescent school boys (aged 11-19 years) in Abha City, Southwestern Saudi Arabia were interviewed and examined for weight and height using standardized techniques. The overall prevalence of obesity and overweight in the present study amounted to 16%. Using logistic regression analysis, lack of exercise practice in the previous week in general [aOR = 1.352, 95% confidence interval (CI) = 1.066-1.941] or in the class (aOR = 1.446, 95% CI = 1.083-1.931) were significantly associated with obesity. The present study showed that obesity among adolescent school boys in Abha City is a public health problem. There is a need for a national program in the country to prevent and control obesity among adolescents. The program should incorporate: dietary management of obesity, promotion of physical activity, health education campaigns and consideration of the possibility of providing facilities for practicing physical activity and exercise in the community.