To bolster the Administration"s case against Iraq, National Security Advisor Condoleeza Rice in the January 23 New York Times cited former UNSCOM chairman Richard Butler"s estimate that a VX missile warhead launched at a major city "could kill up to one million people." However, Rice misrepresents Butler"s analysis, at least as outlined in his book, The Greatest Threat, and neither Rice nor Butler appear to have fully considered the range of factors that can influence the outcome of any given chemical attack. In his book, Butler does not state that a VX warhead would result in up to one million deaths. Rather, he notes that a single 140 liter warhead would contain enough agent to produce that effect. But the fact that a warhead contains a million lethal doses does not mean that a million people would be killed if such a warhead were deployed. As various commentators have pointed out, the outcome of any chemical attack will vary greatly depending on 1) the purity and form of the agent; 2) the dispersal mechanism; 3) weather and meteorological conditions; 4) the terrain of the target area; and, 5) population density and disposition. Elisa D. Harris is a Senior Research Scholar at the Center for International and Security Studies at Maryland.