Of the 463,000 children residing in United States foster care, 29,000 annually exit the system because they have "aged out," are thus dropped from supportive services, and become responsible for their own housing, finances, and health needs. Given histories of maltreatment, housing instability, and parental substance use, youth preparing to exit care are at substantial risk of developing substance use disorders. Unfortunately, access to services is often limited, both before and after exit from care.