OBJECTIVE: To determine the prevalence of overweight and obesity by age, gender and region and to assess the difference between rural and urban populations and determine the trends of the past decade. METHODS: Analysis of nationally represented samples from 2 cross-sectional surveys conducted in 1991 and 2000, containing 5,086 and 6,400 Omani citizens aged >or=20 years. Body mass index (BMI) (weight in kg) divided by height (in meters squared) was calculated using measured height and weight datOverweight was defined as BMI 25-29.9 kg/m2 and obesity as BMI >or= 30 kg/m2. RESULTS: In the year 2000, the age adjusted prevalence of obesity reached 16.7% in men, compared to 10.5% in 1991 (p<0.001). In women, the prevalence was 23.8% in 2000, compared to 25.1% in 1991 (p=0.231). Similarly, the prevalence of overweight increased among men, from 28.8-32.1% (p=0.011) and decreased among women, from 29.5-27.3% (p=0.053). When obesity and overweight were combined, there was a significant increase in men (9.5%; p for the change <0.001) and decrease in women (3.5%; p for the change <0.003). Obesity and overweight combined was markedly more common in the Southern part of Oman (70%) compared to Northern areas (32-57%). People living in urban areas were more obese (21.1%) than those living in the rural communities (13.1%) (p<0.001). CONCLUSION: The prevalence of obesity is high in Oman and has increased predominantly among men. Primary prevention programs are needed to counteract this condition and its cardiovascular and metabolic complications.