Population health care is health information and clinical services provided to individuals of a defined population. From a population health care perspective, quality of care involves the health status of the entire population, and thus issues of access, cost of care, and efficiency matter. In this paper, we describe the definitions of quality health care and the framework for measuring quality, with emphasis on the performance of organizations involved in the delivery and assurance of population health care. We describe quality measurement sets and systems, criteria for the choice of measures, data sources, and how quality measurements are used to improve health care and outcomes from a population health care perspective.