Alcohol could contribute to obesity. The authors examined the relation between drinking patterns and body mass index (BMI) (weight (kg)/height (m)(2)) by pooling cross-sectional data from the 1997-2001 National Health Interview Surveys. Weighted analyses included 45,896 adult never smokers who were current alcohol drinkers. Height and weight were self-reported. In adjusted analyses, alcohol quantity and frequency had opposite associations with BMI. As quantity increased from 1 drink/drinking day to > or =4 drinks/drinking day, BMI significantly increased; in men, it increased from 26.5 (95% confidence interval (CI): 26.3, 26.6) to 27.5 (95% CI: 27.4, 27.7), and in women, it increased from 25.1 (95% CI: 25.0, 25.2) to 25.9 (95% CI: 25.5, 26.3). As frequency increased from low quintiles of drinking days/year to high quintiles, BMI significantly decreased; in men, it decreased from 27.4 (95% CI: 27.2, 27.6) to 26.3 (95% CI: 26.2, 26.5), and in women, it decreased from 26.2 (95% CI: 26.0, 26.5) to 24.3 (95% CI: 24.2, 24.5). In stratified analyses of frequency trends within quantity categories, BMI declines were more pronounced in women than in men, but all linear trends were inverse and significant (p trend < 0.001). In all respondents combined, persons who consumed the smallest quantity the most frequently were leanest, and those who consumed the greatest quantity the least frequently were heaviest. Alcohol may contribute to excess body weight among certain drinkers.