This study examined whether socioeconomic status (SES), measured by household income and educational attainment, moderates genetic and environmental influences on alcohol use. We found that genetic effects were greater in low-SES conditions, while shared environmental effects (i.e., environmental effects that enhanced the similarity of twins from the same families) gained importance in high-SES conditions. This basic pattern of results was found for both income and education and replicated at a second wave of assessment spaced nine years after the first. Our findings indicate that the etiology of alcohol use varies as a function of the broader social context. Thus, efforts to find the causes underlying alcohol consumption are likely to be more successful if such contextual information is taken into account.