Bioterrorism involves the intentional use of biological agents to cause disease or death in humans, animals, and plants. Biological agents are microorganisms that can be weaponized for bioterrorism or biological warfare. They are appealing weapons because they are inexpensive and easy to obtain and disseminate, while being virulent and lacking rapid diagnostics or universal vaccines. Biological agents are categorized based on their priority and potential impact, with Category A agents having the highest priority due to high mortality rates and mass impact potential. To prepare for bioterrorist attacks, countries need more trained epidemiologists, health alert networks, stockpiles of pharmaceuticals, and security measures, as well as physical and immunological protections.