Trust plays a critical role in facilitating health care delivery and calls for rebuilding trust in health care are increasingly commonplace. This article serves as a primer on the trust literature for health policymakers, organizational leaders, clinicians, and researchers based on the long history of engagement with the topic among health policy and services researchers. We conducted a synthetic review of the health services and health policy literatures on trust since 1970. We organize our findings by trustor-trustee dyads, highlighting areas of convergence, tensions and contradictions, and methodological considerations. We close by commenting on the challenges facing the study of trust in health care, the potential value in borrowing from other disciplines, and imperatives for the future. We identified 725 articles for review. Most focused on patients' trust in clinicians (n = 499), but others explored clinicians' trust in patients (n = 11), clinicians' trust in clinicians (n = 69), and clinician/patient trust in organizations (n = 19) and systems (n = 127). Across these five subliteratures, there was lack of consensus about definitions, dimensions, and key attributes of trust. Researchers leaned heavily on cross-sectional survey designs, with limited methodological attention to the relational or contextual realities of trust. Trust has most commonly been treated as an independent variable related to attitudinal and behavioral outcomes. We suggest two challenges have limited progress for the field: (1) conceptual murkiness in terms and theories, and (2) limited observability of the phenomena. Insights from philosophy, sociology, economics, and psychology offer insights for how to advance both the theoretical and empirical study of health-related trust. Conceptual clarity and methodological creativity are critical to advancing health-related trust research. Although rigorous research in this area is challenging, the essential role of trust in population health necessitates continued grappling with the topic.