The goal of this proposal is to establish a multi-disciplinary research Center focused on the theme of opioids and overdose. This will necessarily include vulnerable and underserved populations. To support this general goal, the proposed Special Populations Core (SPC) will build infrastructure to recruit and retain vulnerable and underserved individuals, build capacity in the ethical conduct of research with vulnerable populations, and serve as a centralized resource for training and outreach regarding the conduct of research among individuals most impacted by overdose and opioid-related harms. The near-term, primary mission of the SPC is to support Project Leaders to recruit and retain opioid-involved individuals through multiple venues including emergency departments, opioid treatment programs (OTPs), hospital/perinatal offices and criminal justice (CJ) facilities; navigate the ethical considerations of engaging vulnerable populations, apply for Institutional Review Board approval and convene data safety monitoring boards. The long-term goal of the SPC is to build a sustainable resource to support the practical challenges posed when working with vulnerable and underserved populations across Rhode Island hospital networks and Brown and other local Universities and research institutions. The SPC will provide an array of services and expertise including: facilitating access to patient populations, providing research staff trained in best practices of recruitment and retention and negotiating various recruitment settings, guidance in human subjects protection and regulatory oversight of research conducted among vulnerable populations, and broaden the community of researchers addressing this critical public health issue through outreach and training in these topics, including the critical overlap of CJ involved populations, opioid use disorders and overdose. Dr. Curt Beckwith and Dr. Timothy Flanigan will be the faculty leaders of this Core. They will provide area expertise in working with CJ and substance using populations. Dr. Janette Baird, Scientific Advisor, will provide area expertise in research conducted among individuals with substance use disorders (SUD) in hospital Emergency Departments and Dr. Caron Zlotnick, Scientific Advisor, will provide area expertise in working with pregnant women with SUD. Michelle McKenzie, MPH, Core Manager, will oversee routine operations, manage Core resources, and provide area expertise in recruitment, tracking and follow-up of SUD populations. Ms. Martino, Training Coordinator, will focus on developing educational forum specific to the incarcerated setting. Two Research Assistants will provide recruitment and retention support for Project Leaders.