Bioterrorism : a complex threat / Understanding the threat : actors and capabilities -- The legacy of secret state programs / Evolution of the current threat / The impact of scientific and technological change / Assessing the threat : differing perceptions -- Knowledge gaps and threat assessments / Why do conclusions from the experts vary? / Managing the threat : policy options -- When to cry wolf, what to cry, and how to cry it / More transparency for a secure biodefense / Securing society against the risk of bioterrorism