The Pathways in Autism Spectrum Disorder (ASD) study aims to describe and ultimately to optimize the processes that predict variations in the developmental health (DH) of children with ASD. In Phases I (2004-2009) and II (2009-2014), we employed a multi-method, multi-informant design across 5 Canadian sites to follow children with ASD from their diagnosis (at 2-4 years old) to the beginning of adolescence (10 years). Our team is poised to start Phase III – following this large cohort from age 11 to 17 and examining DH in ASD. We define DH as the social, emotional, cognitive, and physical developmental tasks that all children and adolescents must accomplish. DH can be seen as both a trajectory and a series of achievements or milestones. For example, the socialization domain may reflect changes in social skills over time (a trajectory) as well as achievements such as “having a best friend” (a milestone). Both aspects of DH are examined in this program that addresses 5 questions:1. What DH trajectories unfold in youth with ASD from the preschool years through adolescence? How are these trajectories related to each other?2. What child, family, and service variables and processes are associated with variation in the trajectories and milestones of DH in adolescence?3. In adolescents with ASD, does an intervention aimed at improving self-determination skills (an aspect of cognitive DH) lead to greater improvements in that and other DH domains compared with youth who do not receive the intervention?4. What is the economic burden of ASD in adolescence and what is the incremental cost-effectiveness of specific interventions?5. How do youth with ASD (and their parents) view their lives and needs; how do they experience family, school, and community life, and what does a “good outcome” mean to them as they transition to adulthood?I have led the Pathways team now for almost 20 years with continuous CIHR funding. I am considered a world leader in ASD research and have led several major national and international collaborations. Collectively, the team has expertise in the developmental course of ASD, genetics, measurement, longitudinal data analysis, qualitative research methods, intervention and health services research, policy studies, and health economics. We collaborate with a comprehensive array of “knowledge users” to ensure an integrated knowledge translation (IKT) strategy. To date, we have supported 82 trainees from multiple disciplines. For this proposal, we have also developed a more formal training program focusing on knowledge about ASD, methodological and professional issues, and novel opportunities for trainees to meet with knowledge user partners.Effective interventions are available for young children with ASD, but there is a striking lack of such interventions for adolescents. This gap is partly attributable to the scarcity of natural history studies examining the processes associated with DH variation during this stage. We are confident that our research will provide new knowledge about developmental course and prognosis in ASD – information that is essential for youth, parents and policy-makers. Moreover, we will test an innovative intervention intended to improve self-determination skills that might improve long-term outcomes, and we will identify other new avenues for intervention that could have a lasting positive impact on adolescents with ASD, preparing them for a more enriched adulthood with greater inclusion.