Chronic alcohol abuse is associated with low bone density and high risk of fracture. However, moderate alcohol consumption may help to maintain bone density in postmenopausal women by increasing endogenous estrogens or by promoting secretion of calcitonin. We conducted a prospective study among a sample of 188 white postmenopausal women (ages 50-74) from the Nurses' Health Study who participated in a health examination between 1993 and 1995 that included bone density assessments of the lumbar spine and proximal femur. Long-term alcohol intake was calculated as the average of the 1980 and 1990 measures from a food frequency questionnaire. Women who consumed 75 g or more of alcohol per week had significantly higher bone densities at the lumbar spine compared with non-drinking women (0.951 vs. 0.849 g/cm2, p = 0.002) after adjusting for age, body mass index (kg/m2), age at menopause, use of postmenopausal estrogens, and smoking status. Further adjustment for physical activity and daily intakes of calcium, vitamin D, protein, and caffeine did not alter the results. We also observed a linear increase in spinal bone density over increasing categories of alcohol intake (p = 0.002), suggesting that alcohol intakes of less than 75 g/week may also be of benefit. This positive association was observed among both current users and never users of postmenopausal estrogens. In contrast to the lumbar spine, femoral bone density was not higher among drinkers compared with nondrinkers, although density did increase among drinkers with increasing level of alcohol consumption. Further research is needed to determine whether moderate alcohol consumption can help to protect against spinal fractures in postmenopausal women. This finding must also be evaluated within a larger scope of the risks and benefits of alcohol on heart disease, breast cancer, and hip fractures.