Recent studies in animals and humans have begun to provide insight into the neuropsychopharmacologic basis of alcohol consumption and dependence. Studies involving the serotonergic and opioidergic neurotransmitter systems have shown the most consistent results. Concurrent nosologic developments have led to the identification of subtypes of alcoholism on the basis of their clinical features and patterns of inheritance of alcoholism. These subtypes, which have implications for both the etiology and development of alcoholism, have also been linked theoretically to specific neurotransmitter systems. Consequently, the typologies both provide a hypothetical basis for selecting specific pharmacotherapies and have implications for molecular genetic investigation. This article selectively reviews the literature in these various areas in an effort to enhance understanding of the etiology and development of alcoholism.