Objective: This study provides preliminary evidence on the associations between alcohol consumption patterns and polymorphisms of the alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) enzymes in a Jewish population. Method: Two groups of Jewish men were studied-one group (n = 92) representative of the free-living population of Jerusalem and generally light consumers of ethanol and the other group (n = 53) composed of treatment- enrolled heroin dependent individuals in the same city, most with a history of heavy daily drinking. All participants were interviewed regarding sociodemographic background, present and past alcohol consumption patterns, and familial characteristics including alcohol problems among first-degree relatives. Polymorphisms of the ADH2, ADH3 and ALDH loci were determined for all participants. Results: The less common allele of the ADH2 locus (ADH2*2 allele frequency ≃20% in Ashkenazic and non-Ashkenazic members of both groups) was related to a reduced mean level of peak weekly alcohol intake in the two groups. In multiple regression models adjusting for family history of alcohol problems and other factors, the ADH2*2 allele accounted for 20% and 30% of the explained alcohol intake variance in these two groups, respectively. Results from a logistic regression indicated that the ADH2*2 allele was also related to infrequent drinking in both groups. Evidence for an independent association between the ADH3 polymorphism and alcohol consumption patterns was not found. The ALDH gene was not polymorphic in this population. Conclusions: This report describes for the first time an association between alcohol consumption patterns and a polymorphism at the ADH2 locus in a Jewish population. The relatively high frequency of the ADH2*2 allele may contribute to the seemingly lower levels of alcohol consumption and heightened sensitivity to alcohol observed among Jews.