The link between HIV/AIDS and 'security' is said by many to be well understood, particularly that between the movement and activities of uniformed services and the epidemic. There are strong opinions widely asserted. But recent research undertaken for UNAIDS by LSEAIDS (which brings together. Leading social scientists at the LSE to confront the social and economic implications of HIV/AIDS), reveals that this is not at all the case. The evidence base is patchy-strikingly so. It has been over-nterpreted and even misinterpreted in the rush to respond to a perceived threat by asserting generalizations that do not stand up. In this article the arguments and some of the evidence are reviewed, as are the forces advocating a precipitate response based on poor evidence. The article describes the principles that should underlie an empirically more robust approach. © The Royal Institute of International Affairs 2006.