Medical school admissions is a contentious and high stakes selection activity. Many assessment approaches are available to support selection; but how are decisions about building, monitoring, and adapting admissions systems made? What shapes the processes and practices that underpin selection decisions? We explore how these decisions are made across several Canadian medical schools, and how values shape the creation, monitoring, and adaptation of admissions systems. Using phenomenography (a qualitative method suited to examining variability), the authors analyzed interviews with 10 current or previous heads of admissions from 10 different undergraduate medical education programs in Canada. Interviews were conducted in English and French, and data was collected between 2016 and 2017 (therefore participants no longer hold these roles). Data was coded and analyzed iteratively, focusing on identifying underlying values, and exploring how these values shape admissions practices and considerations for validity. Eight different intersecting values were identified. Of these, four were shared across all participants: critically questioning the process and tools, aiming for equity, striving for better, and embracing the challenges of change. The expression of these values depended on different contextual variables (e.g., geographic location, access to expertise, resource availability), and values shaped how admissions systems were built, enacted, and monitored for quality. Ultimately, values shaped: (1) admissions practices resulting in different candidates being offered admission, and (2) how arguments supporting score interpretation are built (i.e., validity). This study documents various values that influence admissions processes, practices, and quality monitoring. The values that shape what is assessed, how it is assessed, and how fair and defensible practices are conceptualized have significant impact, ultimately determining who is selected. These values--whether implicit or explicit--result in intended and unintended consequences in selection processes. However, these values are rarely explicitly examined and questioned, leaving it uncertain as to which consequences are the intended outcomes of deliberately chosen values, and which are unintended consequences of implicitly held values of admissions systems and their actors.