Planning, drilling, and execution of their emergency management plans helped health care workers meet the challenges presented by the attacks. Valuable lessons were learned to apply in the future, including dealing with the continued threat of nuclear, biological, and chemical terrorism. These lessons can become strategies for health care organizations to follow in preparing for such emergencies. The first lesson is to be sure that all disciplines involved in handling a disaster are represented on the team, including pathology, nutrition, mental health services, medical records, pediatrics, and family support. The second lesson is to be prepared for the influx of a greater number of patients than planned. Plans must be in place to work with the community and neighboring health care organizations to deal with such a situation. Evacuation plans should be reviewed and up to date. Plans for how to open beds in the event of a mass casualty disaster must be made. A structure must be developed that can expand if a second wave of patients arrive. Increased morgue requirements must be prepared for. Foundations for these new contingencies may be found in Y2K plans. Clear procedures for establishing the location of a command center must be outlined, as well as responsibilities, necessary resources, and personnel. Setting up the command center should be practiced frequently. Relationships with other health care organizations and community agencies must be fostered, providing options for opening beds and securing critically needed personnel and supplies. Depending on the disaster, a health care organization could be cut off from the organizations with which it has emergency arrangements. In that case, the organization must be prepared to be self-sufficient and act independently. Every aspect of the emergency management plan must be drilled, including testing and retesting equipment, involving community agencies, the role of clinical staff, setting up the incident command center, evacuating and transporting patients, and requesting and receiving emergency supplies. The final lesson is to be prepared to respond on a regional basis.