There are approximately 25 nations that are believed to be carrying out some form of state-sponsored chemical and/or biological weapons development, as well as at least 2 foreign terrorist groups. Chemical weapons are weapons of terror and intimidation as well as a means of producing casualties and physical destruction. The chemical agents that present a threat to public health are tabun, sarin, soman, cyclohexylmethylphosphonofluoridate (GF), o-ethyl-S-2-diisopropylaminoethyl-methylphosphonothiolate (VX), blood agents, blister agents, and pulmonary agents. Other more commercial agents include heavy metals, volatile toxins, explosive nitro compounds and oxidizers, and flammable industrial gases and liquids. Many forms of lower-level chemical weapons attacks might do no more or less damage than attacks using conventional weapons. It is an illusion that the effects of chemical weapons are always radically worse or more repellant than the damage done by conventional weapons. Most chemical weapons are not easy to handle or deliver, and even nerve gas has to be used in large amounts to achieve high levels of coverage and lethality. Chemical weapons can impose serious problems in terms of detection. The domestic production of weapons will probably only be detectable by receiving a warning through human intelligence, or tracing the flow of key equipment and ingredients which maybe legally and physically impossible. The problems in developing effective interception, defense, and response measures can be compounded by using more than one group of attackers, and by mixing agents that require different kinds of protection and decontamination. Most terrorists will find it difficult to obtain the necessary chemical weapons, in the necessary amounts, and develop an effective delivery system or device. Chemical weapons are the weapons of mass destruction that most first responders and law enforcement agencies feel they are best prepared to deal with. However, serious response problems could occur if a chemical attack should be conducted in enough volume to cover a large area. 3 tables, 3 charts