Cigarette smoking has well known effects on body weight, with current smokers weighing less than never-smokers, and cessation producing weight gain. Use of waterpipe (or "hookah") is increasing in many parts of the world but its effects on body weight are not known. We compared body mass index (BMI) among 2,536 adults (age ≥ 18 years old), who were never, former, current nondaily, or current daily waterpipe smokers, drawn from 2 representative, population-based household surveys of adults in Aleppo, Syria. Overall, 84.1% (n = 2,134) never-smoked waterpipe, 4.6% (n = 116) were former smokers, 9.9% (n = 251) were current nondaily smokers, and 1.4% (n = 35) were current daily smokers. Mean BMI of the sample was 30.2 kg/m(2) (SD = 6.3). Adjusted for cigarette smoking, number of chronic diseases, age, gender, income, and marital status, daily waterpipe users were 2.26 BMI units greater than never-smokers (beta = 2.26, 95% CI = 0.79-3.72), and had nearly threefold odds of being obese (odds ratio = 2.87, 95% CI = 1.06-7.76). Nondaily and former waterpipe users were similar to never-smokers in terms of BMI and obesity risk. Results indicate that daily waterpipe users, compared to never-users, have higher BMI, translating into 6 extra kilograms of weight on average, and are 3 times as likely to be obese.