Background: Obesity is one of the most common health problems in the world and is assuming epidemic proportions in both developed and developing countries. Aim: The present study aimed to provide populationâbased data on the prevalence of obesity and estimation the risk of some of demographic factors associated with obesity. Subjects and Methods: From May 2007 through December 2008, we conducted a communityâbased crossâsectional survey on 3,000 males and females (age ≥ 20 years) in Tehran province. Respondents were asked to give their height and weight in the questionnaire. Body mass index (BMI) is recognized as the measure of overall obesity and calculated as body weight divided by the square body height in meters (kg/m2). Results: The overall prevalence of overweight and obesity was 34.1% (924/2708) and 15.4% (417/2708). The combined prevalence of both overweight and obesity was 51.2% (1387/2708) in males and 57.5% (1557/2708) in females. The mean (SD) BMI for the total population studied was 26.14 (4.71) and it was higher in women than in men (P < 0.001). The overall prevalence of overweight and obesity was 39.5% (376/952) and 11.7% (111/952) in men and 36.9% (548/1458) and 20.6% (306/1458) in women. The multivariateâadjusted odds ratios of obesity showed that higher ages, females, married and low educated subjects had more chance to being obese. Conclusion: This populationâbased crossâsectional survey indicates that the prevalence of overweight and obesity are moderately high in the general Iranian population and must be considered as a significant public health problem at national level especially among women.