This is the second edition of this publication which focuses on the public health aspects of the possible deliberate use of biological or chemical agents. Issues discussed include: the key principles for public health planning, risk assessment, hazard identification and evaluation, risk management strategies, and response planning as part of existing national emergency plans, disease surveillance and early warning systems, the national and international legal framework, and international sources of assistance. Technical annexes cover a range of issues including chemical agents, toxins, biological agents, principles of protection, precautions against the sabotage of drinking water, food and other products, information resources and the affiliation of WHO Member States to the international treaties on biological and chemical weapons.