PROJECT SUMMARY/ABSTRACT Intersectionality frameworks draw attention to health disparities that exist at the intersection of multiple axes of social status and position (SSP). To advance from identifying to intervening upon intersectional health disparities, studies that examine underlying mechanisms such as discrimination are required. Addressing the need for comparable measures of discrimination across multiple SSP for intersectional health disparities research, our team’s R21MD016177 is evaluating the Intersectional Discrimination Index, a set of three measures of enacted (day-to-day and major) and anticipated discrimination. The parent award uses cognitive interviewing and psychometric methods to evaluate the InDI measures in English and Spanish. Advancing intersectional approaches to measuring discrimination is particularly important for HIV research. Barriers to HIV prevention and treatment are driven by intersecting forms of stigma and discrimination based both on SSP and HIV status. Intersectional approaches to stigma measurement and mitigation have been recognized as key to achieving plans to End the HIV Epidemic in the United States. This administrative supplement draws on the HIV Stigma and Health Stigma and Discrimination Frameworks to enhance and investigate the utility of the InDI measures for HIV-related health disparities research. Specifically, we will: (1) create a modified set of HIV-InDI measures to capture HIV-related, as well as SSP-related, discrimination; (2) evaluate the configural, metric, and scalar structures of the HIV-InDI measures; and (3) assess the potential utility of the InDI and HIV-InDI for HIV-related health disparities research through exploratory analyses of whether, and to what extent, disparities in HIV prevention and treatment across intersectional groups may be explained by anticipated and enacted discrimination. To achieve these aims, taking a community- engaged approach, we will conduct cognitive interviews in English and Spanish with people living with HIV (PLHIV) and supplement our quantitative validation surveys by collecting data on HIV prevention and treatment, and recruiting a subsample of PLHIV. The study’s key deliverable will be the HIV-InDI, a set of bilingual measures of anticipated, day-to-day, and major discrimination validated among diverse PLHIV. This expected outcome is aligned with priorities for HIV-related intersectional stigma research towards Ending the HIV Epidemic in the United States identified through a recent NIH expert workshop.