The Promise of Poison: Life in the Field of Pediatric Cancer Treatment is an exploration of the ideologically mediated practices through which people are made into different kinds of participants in processes of pediatric cancer treatment. Since the 1950s, the field of pediatric cancer treatment in the United States has become organized around a multidisciplinary model that the oncologist Sidney Farber dubbed “total care.” In recognition of the various forms of havoc that cancer diagnosis and treatment wreaks on patients and their intimate networks, Farber’s vision calls for multidisciplinary teams of biomedical and psychosocial professionals to provide various caregiving services to both patients and their family members, particularly parents/guardians. Since the time of Farber, many cancer treatment centers throughout the world have adopted some version of his model. In this dissertation, I explore practices of total care at Bay Area Children’s Hospital, which is the site of a major pediatric cancer treatment center in the San Francisco Bay Area. In doing so, I show how models of pediatric cancer care intersect with models of communication and youth in ways that can produce multivalent effects that range from therapeutic to iatrogenic. As young people and their families become positioned as participants in the field of pediatric cancer treatment, their lives become spatially, temporally, and ideologically re-arranged around the demands of particular cancer treatment protocols. In the process, they are not only promised the possibility of healing, but they are also warned about the negative, or iatrogenic, effects of treatment. While the negative effects of biomedical cancer treatment practices are commonly recognized, here I show how psychosocial caregiving practices can also produce harmful effects. One common way in which this occurs is via the subjection of individuals who identify as teenagers to habitats, artifacts, standards, and practices that were designed to facilitate care and communication between adults and young children. Such forms of subjection can enact processes of infantilization, alienation, and stigmatization that inhibit therapeutic interactions. As I will show, the processes that constitute total care are also mediated by ideologies of race, class, and gender that inflect models of care, communication, and youth. Patients and families who inhabit non-white and non-bourgeois identities may be particularly likely to experience the negative effects of total care insofar as it reproduces standards that derive from white, Euro-American, bourgeois ideologies that mark them as “inappropriate” people.