The medical home (also known as patient-centered medical home or advanced medical home) is a composite policy construct representing a set of interventions intended to revitalize primary care practices and improve patient care. As an idealized vision, the medical home has gained the support of stakeholders including employers, health professional societies, health plans, not-for-profit entities, and government agencies. Expectations of the medical home include improvements in healthcare quality, patient experience, provider work-life satisfaction, costs of care, and increased recruitment of medical students into primary care careers. However, multiple definitions of the medical home exist, and the degree to which some often-cited examples of "medical home" successes match these definitions is unclear. Scant evidence currently supports the effectiveness of practice-level medical home interventions for improving quality and reducing costs, but demonstration projects are only recently under way. Carefully specifying the exact components of "medical home" interventions--and interpreting their results in the context of these specifications--will help build a coherent body of evidence to guide the revitalization of primary care.