Before making equipment purchasing decisions, first responders should consider the following emergency response checklist: know the potential contaminants; understand the primary methods of introduction and distribution; investigate specific equipment needs for responding to the threat; develop criteria for selecting appropriate equipment; and establish effective equipment maintenance/donning procedures. The most common chemical agents that could be used in carrying out a terrorist act were developed for military purposes, such as mustard gas, cyanide gas, and the family of nerve agents. Similarly, the most likely biological agents to be used in a terrorist act are those involved in biological seal warfare research programs in the former Soviet Union and Iraq, such as anthrax, botulinum toxin, ricin, and trichothecene mycotoxins. The method of distribution most likely to be used in a terrorist attack is aerosolized dispersion of airborne contaminants within a confined structure or over a wide, populous area. In responding to an aerosolized chemical/biological event, emergency personnel must protect themselves against the contaminant, both internally and externally, while working to aid victims and identify the source and type of the chemical/biological agent used. This article also outlines equipment selection criteria and equipment maintenance and donning procedures.