The lower incidence of Parkinson's disease (PD) among smokers may be explained by a protective effect of cigarette smoke, or by a tendency to avoid addictive behaviors among future PD cases. We conducted an indirect test of the latter hypothesis by comparing the incidence of PD between alcoholics and nonalcoholics in the General Practice Research Database of the United Kingdom. Our case-control study included 1,019 cases and 10,123 matched controls. Overall, we did not find a lower incidence of PD among alcoholics compared with nonalcoholics (odds ratio: 1.09; 95 % CI: 0.67, 1.78).