Underage alcohol use can be viewed as a developmental phenomenon because many kinds of developmental changes and expectations appear to influence this behavior and also because it has consequences for development. Data on alcohol use, abuse, and dependence show clear age-related patterns. Moreover, many of the effects that alcohol use has on the drinker, in both the short and long term, depend on the developmental timing of alcohol use or exposure. Finally, many developmental connections have been observed in the risk and protective factors that predict the likelihood of problem alcohol use in young people. Therefore, efforts to understand and address underage drinking would benefit from a developmental perspective, and the general principles of developmental psychopathology offer a useful conceptual framework for research and prevention concerned with underage drinking.