A developmental framework for understanding and addressing the problem of underage alcohol consumption is presented. The first section presents the rationale for a developmental approach, including striking age-related data on patterns of onset, prevalence, and course of alcohol use and disorders in young people. The second section examines the fundamental meaning of a developmental approach to conceptualizing underage drinking. The third section delineates contemporary principles of developmental psychopathology as a guide to future research and intervention efforts. Strategic, sensitive, and effective efforts to address the problem of underage drinking will require a developmentally informed approach to research, prevention, and treatment.