The properties of potential biological weapon agents for bioterrorism include a consistent effect at low dosage and short incubation period in a population of low immunity, being difficult to treat, able to be produced in bulk, stable in storage and readily disseminated. Possible agents include smallpox, haemorrhagic fever viruses, anthrax, tularaemia and plague. The example of Severe Acute Respiratory Syndrome (SARS) demonstrates the possible consequences of an act of bioterrorism, but also the necessary global response. There is scepticism about the practicability of surveillance schemes and the global elimination of biological weapons though the Biological and Toxin Weapons Convention remains urgent.