This book presents a means of assessing the relative threat from terrorist-use of individual chemical, biological, and toxin agents. It focuses on small-scale, targeted chemical and biological attacks, rather than mass-casualty attacks. The framework considers the elements of access, public health impact, medical treatment, prophylaxis, and dissemination. Other factors that may affect potential use by terrorists include the range of lethality, covert employment of an agent, and the availability of dual-use technologies. The results of this book may be useful in addressing the threat these agents pose, for example by indicating priorities for countermeasure funding. Other uses include weighing the potential effectiveness of policy options, assessing threat reduction approaches to specific agents, and serving as a resource for developing other specialised frameworks.