This column describes several types of data that are useful for interpreting quality-measurement results: standards, means, norms, and benchmarks. Each can be useful in measuring quality, identifying best practices, and improving care. We use a narrow definition of a best practice, adapted from Donabedian's framework of structures, processes, and outcomes of health care (3). In this construct, a "practice" is a process—the means by which a delivery system interacts with and influences patients. A "best practice" is a process that has been demonstrated to produce superior results, such as better patient outcomes.