The attacks of September 11 and the ensuing global war on terrorism have highlighted what many observers had predicted during the 1990s: that collective violence and challenges to the international system by violent non-state actors (VNSA) would become a defining feature of the post-Cold War security environment. It is asserted that new adversaries like Al Qaeda will pursue their objectives whatever the cost and cannot be deterred by the threat of retaliation. These assertions have generated much thinking and debate about the role that deterrence is supposed to play in national security strategy and policy. While it may be true that deterrence will not function with VNSAs in the same way deterrence worked during the Cold War, we believe a revised version of deterrence that we would call Broad Biological Deterrence, or BBD, remains a viable strategy for meeting the challenge posed by VNSAs.