Clinical registries have emerged in the current resource-restricted environment of modern medicine as useful and logical mechanisms for providing health care stakeholders with high-quality data related to the safety, effectiveness, and value of specific interventions. Temporal and qualitative requirements for data acquisition in the context of clinical registries have rapidly expanded as clinicians and other stakeholders increasingly recognize the central importance of this information to the intelligent transformation of health care processes. Despite the potential of more robust clinical data collection efforts to advance the science of care, certain aspects of these newer systems, particularly the prospective, longitudinal acquisition of clinical data and direct patient contact, represent areas of structural overlap between emerging quality improvement efforts and traditional models of human subjects research. This overlap has profound implications for the design and implementation of modern clinical registries. In this paper, the authors describe the evolution of clinical registries as important tools for advancing the science of practice, and review the existing federal regulations that apply to these systems.