Health officials have long feared the use of biological weapons against the U.S. population, but since the September 11 and anthrax attacks, preparation for the possibility of bioterrorism has gained greater urgency. Smallpox is considered one of the most dangerous potential biological weapons because it is easily transmitted, few people carry full immunity to the virus, and there is no effective cure.Worldwide smallpox eradication through vaccination programs was declared by the World Health Organization in 1980, virtually eliminating the possibility of a “natural” outbreak. Officially, small quantities of smallpox virus exist in secure and authorized facilities in the United States and Russia. Recent news reports have linked smallpox weapon capability to Iraq and Afghanistan. Currently, the State Department and Centers for Disease Control and Prevention (CDC) consider the possibility of a smallpox attack to be low. However, the credibility of this threat could change with new intelligence and rapidly evolving world events.