The occasional and opportunistic use of disease in war has a long history, but deliberately manufacturing disease for military use required advances in the biological sciences. Guillemin's account of biological weapons is lucid and concise, providing an excellent guide through the evidence on the past and issues for the future. What is remarkable is not that the science led to military research but that it has led to so little actual use. The best-documented use was by Japanese forces in China during World War II. But even when great powers were prepared to cause mass civilian casualties, they were never quite convinced of the efficiency of biological weapons and nervous about retaliation in kind. The major powers had essentially given up on biological weapons before the end of the Cold War. It is only with the emergence of mass-casualty terrorism and the curious episode of the anthrax letters of October 2001 that the prospect of the deliberate spread of disease was revived and the preparations for such an emergency were stepped up.