Quantity/frequency data on alcohol consumption were obtained by mailed questionnaire from 2,903 same-sex monozygotic and dizygotic Australian twin pairs. Nonmetric multidimensional scaling was applied to these data. A three-dimensional solution was required to account for the observed pattern of twin concordances for alcohol consumption. These results suggest separate determination of abstinence, frequency of consumption and quantity consumed when drinking, rather than inheritance of a single continuum of overall consumption level.