PROJECT SUMMARY/ABSTRACT In the next decade, over one half million youths with autism spectrum disorder (ASD) will enter adulthood. The adult service system is not adequately prepared to meet the needs of this growing population. The burden of coordinating care frequently falls on family members. Siblings are the future generation of caregivers and often become the guardians for their brother or sister with ASD when parents are no longer able to provide care due to illness or death. Yet, siblings are seldom involved in research or support services for the adult with ASD. There is a critical public health need to develop and evaluate programs that enhance sibling involvement in future planning before the crisis of a caregiving transition. The proposed project will develop an innovative program to facilitate adult sibling engagement in family future planning. Siblings FORWARD (Focusing on Relationships, Well-being, and Responsibility aheaD) targets common barriers to sibling involvement in family future planning, including improving family communication around difficult topics, increasing siblings' knowledge of and confidence in accessing ASD service systems, and anticipating and proactively problem- solving barriers to future planning. The program will be delivered collaboratively with community organizations that support adults with ASD. Siblings will participate in individual, personalized modules. A telehealth approach was chosen to address barriers related to geographical separation. Future planning will include input from the adult with ASD. The program will result in a future plan of action written by the sibling, including concrete next steps. The specific aims are to: (1) develop the Siblings FORWARD program, (2) assess feasibility, and (3) assess the outcomes of sibling participation in the program. The program will be further developed through input from a community advisory board, data from sibling and service provider focus groups, and individual interviews with adults with ASD. Then, a small open trial with 5 siblings will be conducted to assess feasibility and further refine the Siblings FORWARD program. Finally, a pilot randomized controlled trial (RCT) (N=36) will be conducted using a control condition (information only). Pre-, post-, and 3- month follow up data will assess outcomes in siblings (changes skills and knowledge, development of a sibling plan of action) and adults with ASD (unmet service needs, quality of life, family social support). Establishing feasibility and assessing outcomes of the Siblings FORWARD program will inform future larger clinical trials. The availability of an evidence-based future planning program will enable community organizations to better serve this aging population. Ultimately, greater sibling involvement in family future planning will result in optimal independence and functioning in adults with ASD through more seamless continuity of care across the life course of the adult with ASD.