The British psychologist James Reason’s insights into the nature of human error and systems theory, which include the “Swiss Cheese” model of accident causation, constitute the fundamental underpinning of the patient safety movement. In this book, Reason discusses approaches to managing complex hazardous systems—including healthcare—and achieving high reliability. Through an examination of the causes of human and organizational errors, as well as singular cases of heroic recovery from errors, this book expands upon the ground covered in Reason’s two other classic texts, Human Error and Managing the Risks of Organizational Accidents.