NO: Smallpox, one of the great killers in human history,1 remains dangerous. Malicious use of smallpox remains a threat because almost certainly clandestine stocks exist.2 3 4 Despite the 33rd World Health Assembly's endorsement of the recommendation that all countries should destroy all live smallpox virus stocks, or transfer them to World Health Organization authorised, maximum containment repositories, we cannot be certain this is the case.2 3 4 The United States believes that the global community should avoid any action that would jeopardise the important research on Variola virus conducted at the two authorised repositories of the virus. Destroying the virus would be irreversible and short sighted, for the reasons spelt out below.