Alcohol contributes more than 10 per cent of the total caloric intake of adult drinkers in the United States. However, the effect of alcohol on body weight has not been adequately studied in the general population. The association between weight and frequency of alcohol consumption was examined in two national cross-sectional surveys: the Second National Health and Nutrition Examination Survey (HANESII; n = 10,929) and the Behavioral Risk Factor Surveys (BRFS; n = 18,388). Linear multiple regression was used to estimate the independent effect of alcohol on weight, adjusting for smoking, age, diet practices, physical activity, race, education, and height. Among men, alcohol had only a slight effect on weight in either survey. However, among women, alcohol was associated with a substantial reduction in weight, which was as large as the effect of smoking. Compared with nondrinkers, women who consumed alcohol 7-13 times per week had the greatest reduction in weight: -3.6 kg (95% confidence limits [CL] = -5.6, -1.5 kg) in HANESII and -3.2 kg (95% CL = -4.9, -1.5 kg) in BRFS. Alcohol confounded the association between smoking and weight, and among women it accounted for nearly 45 per cent of the weight-lowering effect of smoking. Alcohol also diminished the weight-lowering effect of smoking in men, while in women the smoking effect was slightly enhanced. Further studies are needed to understand the causal mechanisms by which alcohol is associated with body weight.