Biological and chemical terrorism is a growing concern for the emergency preparedness community. While health care facilities (HCFs) are an essential component of the emergency response system, at present they are poorly prepared for such incidents. The greatest challenge for HCFs may be the sudden presentation of large numbers of contaminated individuals. Guidelines for managing contaminated patients have been based on traditional hazardous material response or military experience, neither of which is directly applicable to the civilian HCF. We discuss HCF planning for terrorist events that expose large numbers of people to contamination. Key elements of an effective HCF response plan include prompt recognition of the incident, staff and facility protection, patient decontamination and triage, medical therapy, and coordination with external emergency response and public health agencies. Controversial aspects include the optimal choice of personal protective equipment, establishment of patient decontamination procedures, the role of chemical and biological agent detectors, and potential environmental impacts on water treatment systems. These and other areas require further investigation to improve response strategies.