PROJECT SUMMARY In the United States (U.S.) an estimated 300,000 youth, ages 13-17 years, identify as transgender and, over the past decade, increasing numbers of youth have sought gender affirming care. Leading medical organizations— including the American Academy of Pediatrics, the North American Society for Pediatric and Adolescent Gynecology, the Association of American Medical Colleges, and the American College of Obstetricians and Gynecologists—consider gender affirming care in adolescence medically necessary standard of care. Youth who receive gender affirming medical care, for instance, report improved mental health outcomes sustained into adulthood. Despite these findings and medical consensus, increasing numbers of state-level policies restrict or ban medical and surgical care for transgender youth. The outcomes of these policies on transgender and gender diverse youths' psychosocial, mental health, and physical health are unknown. The goal of the proposed study is to determine the feasibility of a longitudinal, mixed methods study that assesses the outcomes of these state- level gender affirming care policies on transgender and gender diverse individuals. We will conduct a mixed- methods feasibility study and pilot with three specific aims: (1) To establish the acceptability of study instruments in the study population and the sustainability of data collection and management procedures over six-months; (2) To determine the feasibility of remote recruitment of transgender youth seeking gender affirming healthcare in U.S. with differing policy contexts, including states with criminalized bans, and those with or without restrictive policies; and (3) To assess initial, descriptive differences in our primary outcomes of interest, including receipt of desired gender affirming care, and to describe qualitative themes. In researching the impact of policy changes on the health of sexual and gender minorities, this project is significant, innovative, and responsive to NICHD priorities (NOT-HD-22-038). This is the first step in developing a timely study to address two critical knowledge gaps: (1) The quantitative and qualitative experiences of transgender individuals under the age of 18, which are underreported in the literature; and (2) The influence of state-level policies on transgender youths' psychosocial and health outcomes. The results of this feasibility study will inform recruitment strategies, data collection and instruments, and sample size estimates for a future R01.