This proposal for a Mentored Research Scientist Award is designed to provide the candidate with training in the behavioral, environmental and neurobiological mechanisms underlying the transitions to drug use and dependence. The proposed career development plan will add new masteries of concepts, principles and methods from several branches of biobehavioral research on drug involvement. The long term goal is to establish the candidate as an independent investigator who will develop and tailor new biostatistical methods that lead to new understandings of transitions from the earliest stages of drug involvement onward to dependence, placing these transitions into context with other antecedent or co-occurring life circumstances, social contexts, and biobehavioral vulnerability traits. Several mentors with complimentary skills will advise the candidate during her career development. Primary sponsor Dr. James Anthony will advise the candidate's training in the area of drug use epidemiology. Cosponsor Dr. Michael Nader and consultant Dr. Kathleen Grant will advise the candidate's training in the area of neurobiology and biobehavioral research on drug abuse. Co-sponsor Dr. Mark Wolfson and consultant Dr. Nikolas Ialongo will advise the candidate's training in the area of community and classroom interventions, respectively. Dr. David Altman will provide assistance on drug abuse policy. Drs. Ken Dodge and Robert DuRant will provide assistance on aggressive and violent behaviors in the context of drug use. The candidate's research plan will focus on addressing gaps in knowledge related to the process by which youths make transitions from early exposure opportunities to later drug use. Consistent with the candidate's prior methodological work, the focus will be on the application and development of methods related to the study of behavior repertoires that are indicators of underlying and otherwise unmeasureable conditions. The candidate will use available data to address research questions that will serve as groundwork for an independent research program that will examine the evolution of drug behaviors and their links with both individual and contextual factors.