 Background: The Australian Parental Supply of Alcohol Longitudinal Study APSALS was established to investigate the short- and long-term associations between exposure to parental alcohol provision, early adolescent alcohol initiation, subsequent alcohol use, and alcohol-related harms, controlling for a wide range of parental, child, familial, peer, and contextual covariates. The cohort commenced with 1927 parent-child dyads comprised of Australian Grade 7 school students, and a parentguardian. Baseline, one- and two-year follow-up data have been collected, and a three-year follow-up is underway. The data collected include child, familial, parental, and peer factors addressing demographics, alcohol use and supply, parenting practices, other substance use, adolescent behaviours, and peer influences. Baseline data show that only 5.8 of the Grade 7 adolescents had initiated alcohol consumption of a whole serve of alcohol. Thus, the cohort is ideal for prospectively examining predictors of initiation and progression of alcohol use, which increases markedly through adolescence. Results to date have highlighted the importance of distinguishing between sipping and drinking of full serves of alcohol in the measurement of adolescent alcohol use as these represent distinct behaviours which occur in different environments. 