Recently incarcerated adults have a high risk of death from opioid overdose and frequently report HIV/HCV transmission risk behaviors, making them a high priority group for health system-based interventions aimed at improving engagement in primary care and utilization of evidence based prevention and treatment services. This project will comprehensively evaluate post-incarceration health care utilization and outcomes for low- income residents with opioid use disorder, HIV and HCV by linking patient-level data from a large prison system and Medicaid enrollment and claims records for a Midwestern U.S. state that has been heavily impacted by the opioid epidemic. The integrated data will then be used to pursue three complementary research aims: 1) To identify individual-level characteristics and comorbidities influencing use of general outpatient care by people with chronic health conditions after they are released from prison; 2) To assess the impact of a systems-level intervention, facilitated pre-release Medicaid enrollment, on the use of post-release outpatient care; and 3) To adapt and evaluate the feasibility and acceptability of a low cost, evidence based transitional care program, called C-TraC, for increasing use of outpatient medical care for incarcerated people with HIV, HCV and/or opioid use disorder. We propose a mixed-methods approach, based on the Replicating Effective Programs (REP) Implementation Theory Model, to adapt a telephone-based, nurse-led case management intervention (C-TraC) for the correctional health care setting. Through key stakeholder interviews and focus groups, we will elicit the perspectives of incarcerated patients, correctional officers and administrators, and prison-based social service and health service providers, in order to develop an adapted C- TraC protocol reflective of locally defined goals and outcomes. Implementation of the C-TraC program across the state prison system will proceed through several rapid-cycle improvement phases, resulting in stakeholder- driven modifications designed to optimize fidelity to core protocol steps and achievement of targeted outcomes. This protocolized implementation approach, together with the novel data resource created through this project, will allow our team to define the optimal target population, staffing requirements and associated costs, and preliminary measures of health impact that will be needed to disseminate the C-TraC to other prison systems, and to conduct a clinical trial to formally assess its effectiveness. If found to be effective in this setting, transitional care interventions such as C-TraC could have a profound public health impact by promoting access to evidence-based opioid treatment for one of the most vulnerable populations in the U.S.