Late adolescence (i.e., the age-group between 16 and 20 years) is characterized by significant changes in neurological and cognitive processes, behavioral and social functioning, and relational and physical contexts as the individual moves toward adulthood. In this age-group, major role transitions affect almost every aspect of life. Moreover, brain development continues-and with it the development of cognitive functions, working memory, emotional and behavioral self-regulation, and decisionmaking. The adolescent's social and emotional development also continues to evolve, affecting interactions with parents, siblings, peers, and first romantic relationships. All of these changes impact drinking behavior during late adolescence, and, in fact, alcohol use, binge drinking, and heavy drinking are particularly prevalent in youth ages 16-20. Determining the common trajectories of drinking behavior in this age-group is important for understanding how adolescent alcohol use helps shape adult outcomes and for identifying risk and protective factors. It also is important to study the short- and long-term consequences of adolescent alcohol use and abuse, including alcohol's effects on the developing adolescent brain and accomplishment of important developmental tasks of this age.