Interestingly, analyses of nonalcoholic sibling pairs in the initial sample produced evidence for a protective region on chromosome 4, in the general vicinity of the alcohol dehydrogenase (ADH) genes.2 A related analysis, using a technique that treats alcoholism as the extreme of a distribution of an underlying quantitative trait,3 showed evidence for linkage to this same region (Williams et al. 1999). This evidence concerns the gene AVP and alcohol dependence.