Flexible response to chemical and biological terrorist threats relies on the ability of first responders to conduct missions in five areas: situation assessment, operations coordination, logistics, health and human services and decontamination. First responders also need to balance this act with the law enforcement investigation required for the criminal act of chemical and biological terrorism. This chapter gives an overview of chemical and biological weapons, the response strategies necessary in case of their usage or attempted usage and the preparedness required, including planning and training, both at the national and international level.