PROJECT SUMMARY/ABSTRACT Patients hospitalized for opioid use disorder-associated infective endocarditis (OUD-IE) have distinctly poor outcomes and high costs. Despite the availably of effective treatment for opioid use disorder and the opportunity to intervene during hospitalization, health care staff tend not to address opioid use disorder during hospitalization for OUD-IE. Existing models of hospital care for patients with opioid use disorder can inform hospital care delivery for OUD-IE patients, though significant adaptation of these models is needed to meet the unique needs of OUD- IE patients related to their prolonged hospital stays. Little is known regarding how to best deploy evidence-based opioid use disorder interventions for medically hospitalized patients. The aims of the proposed study are to: 1) Characterize current practices of health care staff regarding hospital care delivery for OUD-IE patients; 2) Examine the appropriateness, feasibility, and acceptability of implementing evidence-based opioid use disorder care for hospitalized OUD-IE patients; and 3) Adapt an intervention for hospitalized OUD-IE patients and develop a corresponding toolkit of implementation strategies. To accomplish these aims, I will engage health care staff who care for OUD-IE patients at the Hospital of the University of Pennsylvania and will rely on mentorship and collaborators from faculty in the University of Pennsylvania's Schools of Nursing and Medicine. Qualitative data, in conjunction with expert opinion, will be integrated to inform an adapted opioid use disorder intervention for OUD-IE patients and a corresponding toolkit of implementation strategies. Findings from this study will increase the currently limited efficacy of care delivery for hospitalized patients with opioid use disorder and ultimately enhance their outcomes. This program of research and corresponding training activities will facilitate the applicant's long-term goal of pursuing an academic research career committed to improving the quality of care and outcomes for hospitalized people with substance use disorders through implementation science. Specific training goals are to: 1) Understand current practices for care delivery for hospitalized patients with OUD; 2) Acquire a strong foundation in methods for the proposed project and for future research; 3) Develop skills related to designing and implementing new practices in hospitals; and 4) Integrate professional development, grant writing, and scholarship to prepare to be an independent researcher.