As calls are made for a more patient-centered health care system, it becomes critical to define and measure patient perceptions of health care quality and to understand more fully what drives those perceptions. This chapter identifies conceptual and methodological issues that make this task difficult, including the confusion between patient perceptions and patient satisfaction and the difficulty of determining whether systematic variations in patient perceptions should be attributed to differences in expectations or actual experiences. We propose a conceptual model to help unravel these knotty issues; review qualitative studies that report directly from patients on how they define quality; provide an overview of how health plans, hospitals, physicians, and health care in general are currently viewed by patients; assess whether and how patient health status and demographic characteristics relate to perceptions of health care quality; and identify where further, or more appropriately designed, research is needed. Our aim is to find out what patients want, need and experience in health care, not what professionals (however well-motivated) believe they need or get.