Despite significant recent breakthroughs in our understanding of the neurobiological mechanisms involved in substance use (SU) and addiction, progress remains modest toward integrative knowledge on how psychosocial, neurocognitive, and neurobiological risk factors jointly influence SU initiation, escalation, and addiction, and how they are affected in return. The complexity of SU behaviors, their emergence during critical periods of neurodevelopment, and their strong linkages with physical and mental health, demands a comprehensive large- scale, prospective longitudinal study that begins with youth prior to initiation of SU and that incorporates genetic, psychosocial, cultural, neuropsychological, and neuroimaging measures. The aims of this study align with those of the Adolescent Brain Cognitive Development (ABCD) Study Consortium as set forth in RFA-DA-15-015. These are to: (1) Establish how diverse patterns of SU use impact the structure and function of the developing brain; (2) Identify the impact of SU use on health, psychosocial development, neurocognition, academic achievement, motivation, and emotional regulation; (3) Understand how SU and addiction affect the onset, course, and severity of psychopathology, and vice versa; (4) Identify factors that influence trajectories of SU and its consequences; and (5) Establish how use of one substance contributes to use of other substances. As the largest ethnic minority group in the US, Latinos merit a significant position in the enrollment plan for th ABCD study. The Florida International University (FIU) ABCD site will uniquely contribute to achieving these aims and enhance their impact and significance through enrollment of 900 multi-ethnic Latino youth from South Florida who will be 9 to 10 years old at baseline and substance naïve. The vast majority of our sample will be normally developing, but 30% will have a diagnosis of a disruptive behavior disorder (DBD; i.e., ADHD, Conduct Disorder, or Oppositional Defiant Disorder) to increase likelihood of observing initiation and escalation of SU in the sample and to better understand mechanisms accounting for the strong linkages between DBDs and SU trajectories. Furthermore, multidimensional assessment of cultural factors at the individual, intra-familial, and community level in this unique sample, will allow for characterization of how dynamic relationships between cultural factors (e.g., acculturation and biculturalism) influence SU initiation, escalation, and addiction, as well as underlying mechanisms. Participants will complete six assessment waves during the first 5 years of the study, which includes detailed assessments of SU and various psychosocial, cultural, neuropsychological, and neuroimaging measures. In conjunction with the ABCD Coordinating Center, Data Center, and selected sites, this study will reveal how psychosocial (including cultural), neurocognitive, and neurobiological factors dynamically interact to influence SU trajectories during development from childhood through adolescence and into young adulthood. The findings of the ABCD Study will further NIDA's mission to apply cutting-edge science to issues of SU and addiction in order to inform policy and improve prevention and treatment.