Practicing Gender is an ethnographic account of how gender affirming medical care is providedto young transgender people in the United States. Gender affirming care broadly refers to interventions which work to align a person’s social and bodily presentation with an internal sense of gender, when that gender identity differs from the gender they were assigned at birth. The dissertation shows how anticipated futures—of individual youth, of medical practice, and of our understanding of gender itself—shape the treatments available to young people in the present. Drawing on months of clinical observations, attendance at research team meetings and case conferences, participation at national conferences, and over 75 interviews with young people, parents, providers, and other experts, Practicing Gender articulates the temporal and epistemic logics grounding gender affirming interventions. Since the 1990s, gender affirming care has been increasingly available to young people in theUnited States in the form of early social transition, treatment with puberty delaying medication, and access to hormones like estrogen and testosterone. Though this care has often been treated as one cohesive model, the dissertation distinguishes between what I call the logics of “prevention” and “potential” present within the broader umbrella of “gender affirming care.” I argue that many current practices of care emphasize the risk of future outcomes that must beprevented, whether these outcomes are associated with withholding affirmative care or with providing it too broadly. Preventative logics thus are characterized by a concern with two exemplary futures, each which discursively emerges to counter the other; the future marked by suicide and the future shaped by regret. I show what holds these two initially oppositional perspectives together is the way both appeal to anticipated future harms that providers and parents are responsible for preventing. Preventative logics thus encompass very different material outcomes but tend to similarly re-inscribe youth as in need of protection from themselves, and to value gendered care primarily through the ability of that care to reduce unwanted future outcomes. However, I also attend to the ways in which some forms of practice invoke a logic of “potential” alongside or in contrast to that of prevention. While similarly attuned to the future, potential logics manage risk by highlighting the inevitable uncertainty inherent within attempts to know the future, and to know gender. I argue that forms of care which focus on recognizing youths ability to shape their own futures and emphasize the value of gendered embodiment itself are therefore rooted in potential, and suggest pivoting away from prevention towards potential offers more opportunities for gendered medical care to be a part of crafting more livable worlds. The dissertation identifies the clinic as a key node in the web of cultural meaning-making aroundgender identity, without claiming transgender as an inherently medicalized category. Instead, I forward the clinic as a site which consolidates multiple meanings of gender, drawing attention to its porosity and ethnographically illustrating the mechanisms by which contemporary clinical interventions contribute, and respond, to broader notions about the gendered possibilities of the future. Across five chapters, I show how young people and providers manage the pervasive ontological and epistemic uncertainties of gender—the continued questioning of what gender is, as well as how we should know it—by exploring the possible futures enabled through the use of gender affirming interventions. Ultimately, the dissertation shows how medical practices can be a part of building a more affirming world, and offers insight into the relationships between fantasies of the future, scientific knowledge, and the uncertainties of gender.