Fifteen months after releasing its report on patient safety (To Err Is Human), the Institute of Medicine released Crossing the Quality Chasm. Although less sensational than the patient safety report, the Quality Chasm report is more comprehensive and, in the long run, more important. It calls for improvements in six dimensions of health care performance: safety, effectiveness, patient-centeredness, timeliness, efficiency, and equity; and it asserts that those improvements cannot be achieved within the constraints of the existing system of care. It provides a rationale and a framework for the redesign of the U.S. health care system at four levels: patients' experiences; the "microsystems" that actually give care; the organizations that house and support microsystems; and the environment of laws, rules, payment, accreditation, and professional training that shape organizational action.