Hurricane Katrina was one of the largest and most costly natural disasters in U.S. history, and its effects will be felt for many years to come. Though there were many compelling stories of individual acts of heroism in response to the disaster, it is widely agreed that most aspects of the response, including the public health and medical response, fell short of expectations. Hurricane Katrina tested the public health system in terms of its emergency response role; a number of problem areas were exposed in the process. It is important to examine the public health response to Hurricane Katrina to determine what worked well and what did not, so that public health agencies can learn from its experiences and improve its preparedness before another disaster (whether natural or man made) strikes. This study seeks to contribute to this effort by collecting and synthesizing the public health lessons learned from the response to Hurricane Katrina. The authors focused their efforts on areas that they knew were tested by Hurricane Katrina and around which significant problems arose, including the coordination of the medical workforce, the coordination of medical supplies and equipment, communications, and caring for special needs populations. Their findings are based on a review of relevant documents such as government reports, newspaper articles, and national and state-level emergency response plans, as well as a series of interviews with public health officials and other governmental and emergency management personnel in Louisiana, Mississippi, Georgia, Texas, and Florida.