PROJECT SUMMARY/ABSTRACT The US is in the midst of an opioid-related overdose crisis made starkly clear by the unprecedented 100,000 drug overdose deaths in the US in just 12 months (April 2020-April 2021). In addition to the evidence that medication for opioid use disorder (MOUD) reduces morbidity and mortality, data suggest that recovery support services (RSS) enhance treatment initiation and care transitions and may sustain treatment engagement and long-term recovery. Peer RSS (PRSS) are an emerging domain designed to support long-term sustained recovery processes for those with opioid (OUD) and other substance use disorders (SUD). Peers are individuals with lived experience with an SUD who have specialized training in supporting others during their recovery process by providing non-clinical linkages to treatment such as mentorship, referrals for medical illnesses, occupational training, housing, and education. However, the evidence base for PRSS still has gaps in knowledge that hinder their broader adoption of this approach. Addressing PRSS knowledge gaps will inform development and expansion of services and strengthen the system of care that those with OUD may use to initiate and maintain recovery. However, the evidence base for PRSS still has gaps in knowledge that hinder their broader adoption of this approach. The lack of systematic integration and collaboration between researchers and community-based organizations (e.g., PRSS organizations) and an underdeveloped pipeline of future recovery scientists are significant barriers to addressing these empirical and practice gaps. The proposed research network in this application addresses each of these, with a focus on stakeholder engagement in research agenda-setting, enhancing the infrastructure for PRSS recovery science research, and accelerating the growth of the PRSS evidence base in our priority areas and populations, with training and telementoring (i.e., provided through technology) being key approaches to these goals. This application for a Peer Recovery Innovation Network (PRIN) will expand recovery science by developing a research program on PRSS during MOUD treatment using a novel agenda-setting approach and an associated Collaboratory, training and mentoring, and infrastructure development. Our Specific Aims are to: Aim 1: Establish the Recovery Science Collaboratory to include multiple stakeholders, including individuals with lived recovery experience, to accelerate the pace of innovation in recovery science; Aim 2: Establish the Recovery Science Training and Telementoring program within our existing substance use training and telementoring center, to rapidly expand the recovery science workforce; and Aim 3: Conduct process-, outcome-, and implementation-based evaluations of the Peer Recovery Innovation Network and recovery science initiatives in PRIN to optimize the impact, efficiency, and effectiveness for fostering recovery science and monitoring outcomes using defined measu...