For this community-engaged, applied research study, we will develop and pilot-test ADAPT (Alcohol and Drug Choices for People on the Autism sPecTrum), an online class co-designed by and co-taught with autistic people, to help autistic adults with unhealthy substance use. Fewer than half of autistic adults ever received school-based substance use disorder (SUD) prevention programming, leaving them vulnerable to unhealthy substance use. Our prior NIH-funded research demonstrated that some autistic people use alcohol or drugs to cope with anxiety or depression or to fit in socially. Our research team has previously successfully used OAR funding to create and test an online, psychoeducational intervention for autistic adults that was co-developed and co-taught by autistic people (see HEARTS program). Now we propose to use our same approach to address alcohol and drug use. We will: (1) Complete development of ADAPT with our autistic Advisory Board, and (2) Implement ADAPT online with N=30 autistic adult participants to assess immediate and long-term outcomes of substance use knowledge, expectancies, and behavior. This project will produce an evidence-informed curriculum that can be widely shared at no cost to community-based providers.