Biological threat agents are microorganisms and the toxins produced by microorganisms that may cause disease or death in humans, animals, or plants and include bacteria, rickettsiae, viruses, and fungi. Chemical threat agents are any toxic chemical or its precursor that may cause death, injury, temporary incapacitation, or sensory irritation through its chemical action. Chemical weapons of various types had been utilized by militaries throughout history to gain an advantage over their adversaries. The use of more “modern”-type chemical warfare agents was suggested and researched in the nineteenth century, but most military leaders were reluctant to deploy them. Local first responders are the first line of defense whether chemicals are released in an industrial accident or by a terrorist act. While the threat of the use of chemical threat agents by terrorists is ever present, it is likely that the greatest threat, particularly from a biological perspective, is, or will be coming, from the natural environment and mankind’s interaction with it.