Genetic effects from the aldehyde dehydrogenase gene localised on human chromosome 12 have been shown to have a major effect on the development of alcoholism in Far Eastern populations. This effect is caused by a point mutation in an exon of the aldehyde dehydrogenase gene which inactivates the enzyme, is dominantly inherited and effectively divides the population into those at risk and those at very little risk of developing alcoholism. This metabolically induced aversion to alcohol has not been shown in white European populations but it is likely that the alcohol dehydrogenase genes on chromosome 4 affect some aspects of alcohol consumption both in the Far East and in European populations and that the dopamine D2 (DRD2) gene also plays a part in a subgroup of individuals. The human genome project and recent genetic linkage studies have brought us to the threshold of a much deeper understanding of how genetic and environmental factors interact in alcoholism. The well known clinical observation of comorbidity of alcoholism with anxiety, depression and antisocial personality will soon be understood in the context of genetic effects from specific genetic susceptibility loci. This genetic research will reinvigorate clinical epidemiology by helping to identify environmental factors much more accurately and will enable both improved treatment and prognosis.