Little is known about the role of alcohol in determining change in body weight. In this paper, the authors examine the relation between alcohol intake and body weight in 7,230 US adults aged 25-74 years who participated in the First National Health and Nutrition Examination Survey (1971-1975) and who were reweighed 10 years later (1982-1984). Both cross-sectional and prospective analyses were adjusted for age, race, height, education, health status, smoking status, diet status, physical activity, and total nonalcoholic caloric intake. At baseline, women who reported at least one drink per day weighed 2.3 kg less than nondrinkers (95% confidence interval (CI) -0.4 to -4.2). Little relation was observed between body weight and alcohol intake cross-sectionally among men. Prospectively, both men and women drinkers tended to gain less weight than did nondrinkers (p = 0.006 for trend in women, p = 0.11 for trend in men). Drinkers also had more stable weight over the 10-year follow-up period. Drinkers were less likely to have major weight gain or loss (gaining or losing > or = 10 kg) than were nondrinkers. Compared with nondrinkers, for those who consumed 1-6.9 drinks per week, women had an odds ratio (OR) = 0.7 (95% CI 0.5 to 0.9) for major weight gain and an OR = 0.7 (95% CI 0.5 to 1.1) for major weight loss, while men had an OR = 1.0 (95% CI 0.6 to 1.6) for major weight gain and an OR = 0.7 (95% CI 0.5 to 1.2) for major weight loss. For those who consumed > or = 2 drinks per day, women had an OR = 0.5 (95% CI 0.3 to 1.0) for major weight gain and an OR = 0.8 (95% CI 0.4 to 1.6) for major weight loss, while men had an OR = 0.9 (95% CI 0.5 to 1.6) for major weight gain and an OR = 1.0 (95% CI 0.6 to 1.7) for major weight loss. These data suggest that alcohol intake does not increase the risk of obesity.