Summary/Abstract Young adulthood is a challenging time focused on making important decisions that can either facilitate or hinder independence across a variety of domains. The CHOICE-STRATA Study (CHOICE STudy of Racial diversity in AOD use during the Transition to Adulthood) has assessed alcohol and other drug (AOD) use and functioning in numerous domains (e.g., social, economic, health) across 13 waves of data in youth from age 10 to age 24 (R01AA016577, R01AA020883, R01AA025848), with retention rates averaging 84% across the 12 waves completed to date, and 91% from age 18 (waves 8-12). The proposed study, STRATA-XP (eXPanded), provides an important opportunity to follow this large and racially/ethnically diverse cohort into young adulthood (ages 25-28), a unique developmental period for which there are few contemporary longitudinal studies of AOD use. This application responds to NOT-AA-20-017: Epidemiology and Prevention in Alcohol Research, focused on understanding the developmental trajectories of alcohol use, risky drinking, and alcohol use disorders and the correlates of "maturing out" of heavy drinking. We propose to conduct 4 additional annual surveys from age 25- 28 (N=2,500) and address the following aims: Aim 1a: Identify trajectories of alcohol use (as well as tobacco, cannabis, and other drug use) from age 10 into young adulthood. 1b.Examine effects of individual factors (e.g., resistance self-efficacy), peer factors (e.g., time spent around peers who use) and neighborhood factors (both subjective and objective, including alcohol and cannabis outlet density) on AOD use trajectories. Aim 2: Examine how AOD use trajectories across adolescence and emerging adulthood predict outcomes through age 28 in three core domains: 1) risk behaviors (e.g., AOD use and disorder, risky sexual behavior, delinquency), 2) health-related quality of life (e.g., mental, physical, social), and 3) adult role functioning and transitions (e.g., employment, relationships and family formation, life satisfaction). Aim 3:Examine how adult role functioning and transitions, such as pursuing a career and parenting, longitudinally predict subsequent changes in AOD use and other risk behaviors, as well as health-related quality of life, in young adulthood. Aim 4: Provide an understanding of potential across race/ethnicity, gender, and educational attainment that may occur across the AOD trajectories and the factors associated with these trajectories. Continuing this work will move the field forward by providing a better understanding of developmental patterns, antecedents, and consequences of AOD use among today's young people as they transition into young adulthood.