PROJECT SUMMARY Ongoing research to improve assessment of sex and gender among transgender participants remains a key priority. In order to ensure research on transgender health is effective, impactful, and valid, meaningful and affirming measurement of gender and sex characteristics is essential. Current recommendations emphasize use of a two-step method which asks for individuals' sex assigned at birth and current gender identity. However, two-step methods which have been tested remain poorly attuned to intersex experiences and experiences of non-binary gender identity. In addition, alternative two-step methods, three-step methods, choose-all-that-apply methods, and open-response methods have all been proposed as alternatives in recent years. As a result, it is imperative that current two-step methods are effectively refined and receive appropriate comparative testing relative to other proposed methods. Moreover, gendered experience is contextual; cultural, temporal, and other forms of gender diversity are not captured by many two-step methods currently in use. Tailoring our methods to improve validity for transgender and gender-diverse individuals who do not fit the normative, binary experience of gender in the United States is therefore essential. Finally, while questions of measure validity are critical to this work, it is also important to consider the ways in which transgender and gender diverse individuals experience the act of reporting sex and gender on survey questions itself, and in particular, the ways in which measures of sex and/or gender may be experienced as stigmatizing or affirming by transgender and gender diverse respondents. Stressors related to discrimination and victimization tied to SGM status are strongly associated with health disparities, whereas multilevel experiences of affirmation are known to promote transgender health on the individual and population levels. Therefore, we must consider that measures of sex and gender which reinforce normative conceptualizations of these constructs have the potential to act as microaggressive minority stressors, and to contribute negatively to the health of transgender and other gender diverse respondents. This project, a supplement to an existing, mixed-methods study aimed at improving measurement of sex, sexual orientation, and gender identity (SSOGI) through community- engaged methodologies, addresses both the current gaps in the literature regarding the validity of two-step and alternative measures of sex and gender, and advances a new line of inquiry which centers the importance of trans affirmation in research. In addition, drawing on the theory and methodology of intersectionality, this project will advance understanding of how best to measure and respond to health inequities for transgender and other gender diverse communities of color. Through qualitative and quantitative testing, we will better validate existing measures of sex and gender in more diverse populations, and ...