Recent acts of terrorism have ranged from the dissemination of anthrax spores to intentional contamination of food to the release of chemical weapons to suicide attacks using explosives. The prediction of such events is difficult, if not impossible. The recent attacks that have generated massive numbers of injured and dead may signal the crossing of a new threshold from multi-casualty events to the use of weapons of mass destruction. Consequently, the medical and healthcare infrastructure must be able to prevent and treat illness and injury resulting from such events. Thus, a first step in improving the preparation for and responses to such events must include a sustained commitment to training physicians, nurses, identification specialists, pathologists, and other first responders. The rapid spread of SARS gives reason to believe that the distribution of such agents has potential advantages over the use of other weapons. Investments in the public health and healthcare systems provide the best defense against terrorism.