This document discusses bioterrorism and bioterrorist agents. It defines bioterrorism and provides examples of historical bioterrorism incidents. It describes the three categories of bioterrorism agents according to the CDC based on their ease of transmission and potential for mortality. Priority agents are characterized by their ability to infect via aerosol and cause high morbidity and mortality. Sources of potential bioterrorism and impacts on direct infection, the environment and economy are reviewed. The anthrax attacks in the US in 2001 are summarized.