The opening years of the new millennium have presented a new and worrisome possibility to the public, including travellers: the threat of deadly infectious diseases from biological agents being deliberately released. The possibility of bioterrorism had always seemed remote but the recent anthrax attacks by mail have made this threat of immediate relevance. The deliberate use of Bacillus anthracis with the intent to harm civilian populations has raised public health concerns about potential exposure to intentionally released Variola virus and other biological agents. There is an urgent need for countries to examine their preparedness to respond to biological weapons attacks. Given the emotional shock of even an alleged threat of a biological release, it will be wise for governments to consider how to address such dangers as an integral part of the national response to other threats to public health and well being. Physicians and other health professionals, including those providing guidance to international and domestic travellers, need to have a clear understanding of the possible agents and the appropriate therapy or prophylaxis. This paper attempts to give a perspective on the threat of bioterrorism, the consequences of its use, the likely biological agents that may be used, and the clinical presentation and management of diseases caused by some agents most likely to be used.