Autism Spectrum Disorder (ASD) affects roughly 1 in 88 US children. Service delivery can be complicated during transition from youth to adulthood, when youth must begin to manage their own healthcare. Essential skills include making appointments, communicating with providers, and understanding and following medication regimens. Medication regimens may be especially important to the 30-50% of youth with ASD who also experience symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD). These youth have greater difficulty in day-to-day life, higher levels of psychopathology, lower quality of life and poorer adaptive functioning. They are more likely to use psychotropic medications (58%) compared to youth with ASD or ADHD alone (34% and 49%, respectively). Transition and adherence challenges can peak at the same lifestage among later adolescents and college students. Disruption or cessation of medication routines among youth with ASD/ADHD leaves them vulnerable to otherwise preventable setbacks in previously-achieved skills. UNMET NEED: Ever-increasing prevalence estimates of both ASD and ADHD mean that increasing numbers of youth are affected by these disorders as they enter adulthood. The changing health care environment demands patient engagement and shared decision-making, yet patients remain largely on their own to learn essential skills and find supportive resources. This may pose a particular challenge for higher-functioning patients with ASD/ADHD. OBJECTIVE: In this Clinical Trial Planning Grant, we will develop and pilot a manualized intervention for Transition to Medication Self-Management (T-MSM) for higher-functioning youth with ASD/ADHD, to arm youth with the skills and tools they need as adults to navigate the healthcare system and successfully transition to self-management of medications. Our three Aims are: 1) a community-based survey to assess patient/family needs and test feasibility of recruitment; 2) development of a manualized curriculum, using a participatory approach that involves patients; providers; family and scientific advisors; and 3) a pilot RCT to test feasibility of our intervention and obtan preliminary data on the impact of the T-MSM intervention, compared to an enhanced standard of care (ESC) control intervention. INNOVATION: We will prepare youth with ASD with tools to self-manage their medication use and related healthcare. Consistent with national goals for health literacy and patient empowerment --in a climate where demand for providers exceeds supply --it is essential to help patients engage and participate in their medical management. SIGNIFICANCE: Upon completion of these aims, we will have a comprehensive community-wide sample frame from which we can rapidly draw a diverse, representative sample for a larger trial, and an engaging, effective, and efficient manualized program and supportive resources. We will be prepared to conduct a larger RCT, among youth with co-occurring ASD/ADHD, to assess the impact of T-MSM program; transition outcomes; and the duration of effects on self-management of medications and related healthcare in adulthood.