The management of flow is a familiar concept in manufacturing. Henry Ford used it to create the automobile age, and Toyota has honed it to create manufacturing processes that function at previously unimagined levels of reliability. The management of flow is in its infancy in healthcare but holds the promise of achieving significant improvements in efficiency and quality. The complexity of healthcare has increased dramatically in the past 50 years, but we remain relatively unsophisticated in the design of our key processes. Why have we retained this cottage industry approach even as we have become the single largest segment of the American economy? The answer may lie, in part, in the notion that each patient is unique and so requires a unique approach. Our failure to implement consistent, reliable processes may also have its roots in the fervently held value of physician autonomy. We have been unable to shed the paradigm of the hospital as a workshop where physicianartisans practice their craft, each in their own way. To be sure, medicine is part art and part science, and the knowledge and skill of individual physicians is of central importance in caring for patients. But a culture in which individual autonomy trumps known best practices creates a dangerous paradigm that lies at the root of the inconsistent quality that plagues healthcare today. Certainly, patients have individual needs; they are not widgets. But patients being treated for similar conditions are much more alike than they are different. Doctors and other caregivers must be able to vary from standard care processes to meet the needs of individual patients and at the same time ensure that such variances are purposeful and thoughtful. To create the opportunity for a caregiver to vary intelligently from a care process, we must first remove unwanted, random variation from the process. Anyone familiar with the workings of hospitals in the United States will admit that they are very far from that ideal. That is why the early work on flow that has begun under the leadership of the Institute for Healthcare Improvement (IHI) and described by Haraden and Resar in this issue of Frontiers is so important. Also discussed in this issue are the efforts of two hospitals that serve as case studies on solving flow problems. They offer important insights into the rationale for focusing on patient flow, the benefits to be gained, and the barriers to be overcome. Baptist Memorial Hospital in Memphis, Tennessee, undertook its work on flow to address a shortage of inpatient bed capacity that was causing ambulance diversions, a problem familiar to many communities in the United States. Through a combination of process redesign and creation of additional capacity (a fast-track unit in the emergency department), Baptist achieved impressive gains in throughput but also achieved measurable improvements in quality. For example, it was able to reduce the percentage of patients leaving the emergency department (ED) against medical advice from a baseline of 5 percent to 1.4 percent. St. John's Hospital in Springfield, Missouri, achieved remarkable improvements in patient flow through very simple process changes. For example, St. John's decided to dedicate one of its operating rooms for add-on cases. In the face of a perceived shortage of available operating room capacity, taking one of the rooms out of the inventory available for block scheduling required some courage and consensus building. The results were rewarding: a 5 percent increase in throughput during peak hours and a 45 percent reduction in the need for operating rooms in the off-hours with improved predictability of staffing requirements for the surgical nursing units. Similarly, something as simple as a faxed report form from the ED to the cardiac care unit reduced the time required to move a patient from the ED to the unit by 67 percent. If improvement in patient flow can produce more efficiency, better outcomes, and better staff and patient satisfaction, why are we seeing so little work in this area? …