Harmful alcohol consumption, particularly alcohol use disorder (AUD), is a worldwide health priority, contributing substantially to global morbidity and mortality. The peak age of onset of AUD is 18, thus a deeper understanding of the adolescent experience is vital if we are to identify modifiable risk factors and intervene early in the developmental course of this disabling disorder. The proposed study responds to a recent urgent call for high quality, long-term prospective cohort studies to better understand the public health burden of adolescent drinking. Critical unanswered questions include: How soon after drinking initiation do AUD symptoms begin to emerge? Which symptoms come first? Do the symptoms unfold in a predictable pattern? In what ways do the emerging symptoms interact with individual, peer, family and environmental risk factors to predict the transition to disorder? The proposed RADAR project draws together a team of researchers with experience in longitudinal cohort research to examine the prospective development of AUD symptoms over the adolescent years. We will capitalise on an existing cohort of 1911 community-based mid-adolescents who have completed a baseline and three annual follow-up assessments as part of a naturalistic longitudinal study. We will interview these adolescents from around 16 years of age every six months for four years to derive monthly histories of both alcohol use and AUD symptomatology, along with a comprehensive battery of risk and protective factor scales hypothesised to predict the emergence and course of AUD. The results of this study will inform not only the natural history of AUD but will be used to identify specific targets for prevention and early intervention of AUD.