PROJECT SUMMARY/ABSTRACT This study will examine how drug-related stigma influences the utilization of HIV prevention and testing programs among people who inject drugs (PWID) in the context of ongoing HIV outbreaks in Appalachia. The opioid crisis has contributed to high levels of injection drug use in rural communities, leaving them highly vulnerable to HIV outbreaks. Scaling up evidence-based HIV prevention and testing programs is critical for averting these outbreaks but even where these programs exist, often they are not used by PWID. Drug-related stigma may pose a substantial barrier to engaging in these services, especially in rural communities where anonymity and confidentiality are difficult to maintain. However, there is limited research on how drug-related stigma and its individual constructs (e.g., enactedstigma, anticipated stigma, internalized stigma) affect program uptake among PWID. Our study will used a sequential mixed methods approach to fill these knowledge gaps by (1) exploring the ways in which stigma influences the utilization of HIV prevention and testing programs among rural PWID, (2) adapting and validating an existing stigma scale, the Substance Use Stigma Mechanisms Scale (SU-SMS), for rural PWID, and (3) characterizing the types and sources of stigma that serve as barriers to HIV prevention and testing program participation in this population. The study will be conducted at two sites in West Virginia, which is the location of ongoing HIV outbreaks fueled by injection drug use. In Phase I of the study, we will conduct qualitative interviews with PWID (N=40) and healthcare providers (N=24) to provide insight into how stigma is operationalized in the context of HIV services utilization. In Phase II, we will conduct a survey of PWID (N=300) to adapt and validate the SU-SMS. Then, we will model the association between individual stigma constructs and HIV prevention and testing program use while also considering other structural- and individual-level factors that influence healthcare utilization. The resulting information will assist us in targeting, developing, and testing novel stigma-reduction interventions designed to improve rural PWID engagement in HIV prevention and testing services, with the ultimate goal of reducing HIV transmission among PWID in rural communities.