As previous research has observed, medical students and physicians alike confront vast amounts of knowledge in their education and practice, such that no one clinician can know everything there is to know about biomedicine. Even before clerkships, medical students learn to cope with this impossibility by prioritizing certain information based on its perceived utility for exams and clinical practice. Many factors can shape this process, including teamwork, wherein individual medical students rely on one another to address gaps in knowledge at the level of the group. This paper will draw on qualitative data from two allopathic medical schools in the American Midwest to demonstrate that peer-to-peer learning, a widely utilized pedagogical modality in North American medical schools, is amongst the earliest places where future physicians learn how to rely on their peers in the profession as they make choices about what to know and what not to know about biomedicine: cultivating a culture of “intraprofessionalism” between students with different knowledges and values, as they prepare to enter the same profession. The paper will also consider how differences in the student populations at two field sites impact intraprofessional development. Drawing on scholarship of peer-based learning strategies and the sociology and anthropology of medical education, the authors argue that peer-to-peer learning is a key site in the professional socialization of medical students toward the effective management of medical knowledge.