Obesity among children is an increasing concern. This cross-sectional study in 2006 determined the prevalence and demographic characteristics of overweight and obesity in children in the Eastern province of Saudi Arabia. A total of 7056 children (aged 2-18 years) were selected from schools and the outpatient department of a hospital. The overall prevalence of overweight was 19.0% and of obesity was 23.3%. More than 50% of children between 14 and 18 years had weight above the 85th percentile. More males than females were obese by ages 14-18 years (35.6% versus 19.2%). Saudi and non-Saudi nationalities had the same distribution of body mass index. Interventions to encourage healthier lifestyles for children are needed at the national level.