Project Summary People living with HIV (PLWH) who use drugs are among the most vulnerable in the HIV continuum of care, exhibiting low rates of retention in care and poor clinical outcomes. HIV and hepatitis C (HCV) often co-occur due to shared vulnerabilities and routes of transmission including injection drug use, which is also associated with risk for opioid overdose. PLWH who use drugs experience anticipated and enacted stigma in healthcare settings, which contribute to poor clinical outcomes. Harm reduction (HR) is an approach that aims to reduce the negative effects of risky health behaviors without necessarily eliminating them completely and is an effective way of engaging people who use drugs into care. Though often thought of as structural approaches, such as syringe services, harm reduction is also a relational approach to care that focuses on non-punitive, autonomy-building relationships between patients and providers. This R01 will explore the degree to which structural and relational HR approaches to care buffer experiences of stigma for PLWH who use drugs in HIV primary care settings and improve the quality of patient-provider relationships as well as clinical outcomes. The study will explore healthcare providers' attitudes towards working with PLWH who use drugs and the ways these relate to their acceptance and practice of structural and relational HR. This will be accomplished via web- based surveys (n=125) and qualitative interviews (n=20) with healthcare providers in Pittsburgh, PA and Birmingham, AL. These methods will utilize a multi-level lens, engaging multiple provider types, such as social workers, nurses, and physicians working in HIV primary care teams. Using an intersectionality framework, the study will also assess the degree to which patients' perceptions of their HIV providers' HR care are associated with anticipated and enacted stigma in HIV primary care settings and with clinical outcomes. Data will be collected by surveying PLWH who use drugs (n=500) to explore if structural and relational HR mitigate stigma, improve the patient-provider relationship, and ultimately improve clinical outcomes as measured via electronic health records data including HIV viral load, retention in HIV primary care, HCV sustained virologic response, medication adherence, and retention in care for Medications for Opioid Use Disorder and/or in behavioral health treatment for substance use disorder. Study methods will include an evaluation of the psychometric properties of the Patient Assessment of Providers Harm Reduction Scale (PAPHRS), a novel scale to measure relational HR care. Finally, the study will apply human-centered design approaches to engage stakeholders in reviewing findings from providers' and patients' experiences of HR care to develop an intervention to operationalize HR care in HIV primary care settings. A preliminary exploration of the feasibility, acceptability, and appropriateness of the newly-developed intervention will be conducted with HIV providers. Ultimately this research trajectory aims to improve adherence to care and health disparities for PLWH who use drugs.