Cigarette smoking and caffeine consumption are associated with a decreased incidence of Parkinson's disease (PD). This inverse association may result from neuroprotective effects of cigarette smoke and caffeine, or from a disinclination of future PD patients to engage in habituating behaviors. We investigated the association between consumption of alcoholic beverages, another potentially habituating behavior, and risk of PD in two large prospective cohorts Nurses' Health Study, and Health Professionals' Follow-up Study. We detected 415 new cases of PD during follow-up. Compared with nondrinkers at baseline, the relative rate (95% confidence interval) was 1.0 (0.8-1.3) for drinkers of less than 5 gm/day, 1.0 (0.8-1.4) for 5 to less than 15 gm/day, 1.1 (0.8-1.6) for 15 to less than 30 gm/day, and 0.7 (0.5-1.2) for 30 gm/day or more (p for trend = 0.45). Consumption of wine or liquor was not associated with the incidence of PD. Compared with those who consumed beer less than once per month, the relative rate (95% confidence interval) was 0.7 (0.5-0.9) for one to three drinks of beer per month, and 0.7 (0.5, 0.9) for one or more drinks of beer per week. The risk of PD was similar in individuals who usually consume moderate amounts of alcohol and in abstainers.