Abstract Alcoholism has been described as a behavioral condition comprised of symptoms of alcohol dependence and the psycho‐socio‐biologic consequences of chronic alcohol dependence. Progress in clarifying the role of genetic factors in explaining differences in onset of dependence upon alcohol, frequency of consequences of chronic alcohol use, and transmission of patterns of alcoholism within a family pedigree has been based upon use of diagnostic methods that reliably and validly separate alcohol dependence from alcohol abuse. Twin methods, which control for genotypic variation, and adoption studies, which control for differences in rearing, have provided significant support for a genetic vulnerability hypothesis for development of alcoholism and a genetic heterogeneity hypothesis for type of alcoholism. The author reviews data from basic and clinical investigation of two subtypes of alcoholism: one associated with antisocial personality, and one that is “familial” (family‐history‐positive alcoholism). ...