The CDC National Center for Health Statistics (NCHS) estimates that for the 12-month period ending September 2021 in the United States, (US) there were 99,543 drug overdose deaths. Kentucky had the 2nd highest age-adjusted drug overdose fatality rate (51.5 deaths/100,000 persons) in the US in 2020. To address the high numbers of drug overdose fatalities, effective strategies are needed to link persons in SUD treatment or those with illicit SUD not yet in treatment with recovery support services (RSSs) to build and maintain recovery, and reduce resumption of illicit substance use and drug overdoses. Access to Recovery (ATR) is a linkage strategy supported by Substance Abuse and Mental Health Services Administration (SAMHSA) that was implemented by Kentucky in 2019 to link vulnerable populations with opioid and/or stimulant SUDs to RSSs using a voucher system and re-link clients to RSSs following resumption of substance use. The Kentucky ATR (KATR) strategy is a 25-county program that links county residents at or below the 200% national poverty level who have illicit SUDs and are in treatment or early recovery to evidence-based RSSs such as recovery housing, and to other RSSs. Priority KATR clients set by KATR are justice-involved, veteran, pregnant/ postpartum, and parenting populations. To address the gap in accessibility of RSSs that often occurs in vulnerable populations, the KATR linkage approach uses vouchers as a linkage strategy for individuals in SUD treatment who have no other funding options to acquire critical RSSs. As such, KATR’s linkage through vouchers is a “last resort” approach for linking to RSSs. The purpose of this proposal is to perform a rigorous process and outcome evaluation of this last resort voucher strategy of linking by accomplishing the following specific aims: Specific Aim 1: Conduct a process evaluation of the KATR linkage strategy to determine whether the KATR strategy is acceptable and accessible to vulnerable populations with illicit SUD who are linked to RSSs; identify barriers and facilitators to KATR implementation; and assess the extent to which the KATR strategy was implemented as designed. Specific Aim 2: Conduct an outcome and impact evaluation of the KATR linkage strategy. Specific Aim 3: Evaluate the long-term effectiveness of implementing vouchers as a linkage strategy in a population requiring RSSs when no other funding sources are available. A within-subjects design will be used to test the effectiveness of the KATR voucher linkage approach to reducing the risk of nonfatal and fatal overdoses by increasing an individual’s recovery capital; reducing resumption of illicit substance use; and promoting relinking to RSSs if illicit substance use is resumed. Study results may enhance current state ATRs that serve individuals experiencing similar SUD health access disparities.