PROJECT SUMMARY / ABSTRACT Sexual and gender minority (SGM) people have higher rates of HIV and other sexually transmitted infections, suicidal ideation and attempts, obesity, cancer, poor mental health, and smoking and are at increased risk for poor health outcomes compared to non-SGM people. Yet how these disparities might be mitigated and prevented is unclear, in part because research among SGM populations suffers from challenges in capturing sexual orientation and gender identity (SOGI). These challenges include the ability to achieve accuracy when collected and to use questions that resonate and are understood by both SGM and non-SGM people. The existing evidence on accurately capturing SGM status lacks racial/ethnic diversity and skews toward mostly white SGM samples. Further, HIV prevention and treatment research efforts have evolved to target “key populations,” such as men who have sex with men (MSM) and transgender women who are at elevated risk for HIV transmission and acquisition. Transgender women and MSM, therefore, may be more familiar with survey questions that seek to assess SOGI than other SGM individuals and groups considered less at risk for HIV (e.g., lesbians, bisexual women, transgender men, non-binary people). Additionally, transphobia and homophobia are often experienced in and can contribute to a context of HIV stigma and may impact the ways in which SGM status is perceived and captured in HIV-specific settings. The intersections of racism and transphobia and/or homophobia can exacerbate HIV-related stigma, also contributing to measurement hurdles. Differences in the ways in which SGM individuals identify across US regions and cultures represent another barrier to capturing accurate SGM status in data collection. To determine the best way to differentiate SGM people from non-SGM people in population research, it is essential to assess such measures in racially/ethnically diverse populations and unique contexts. This supplement leverages the data and infrastructure of two NIH-funded studies (parent grant: U01HL146242; PI: Tien and R21MD015878; PI: Obedin-Maliver) with the primary goal of expanding measurement testing to the MACS-WIHS Combined Cohort Study, a prospective cohort of geographically and racially/ethnically diverse individuals living with or at risk of HIV in the US. This supplement's aims are to: (1) Assess the function and performance of an SGM status screening question and SOGI question sets in a racially/ethnically diverse US cohort of people living with or at risk for HIV via the MWCCS; and (2) Determine the function and performance among SGM and non- SGM people who are (a) HIV-negative and HIV-positive and (b) in HIV-specific and non-HIV-specific study settings in the MWCCS, The Population Research in Identities and Disparities for Equality (PRIDE) Study, and the Health eHeart (HeH) Study. The aims of this supplement are aligned with NHLBI's objective to “investigate factors that account for differences in...