This paper draws together several years of work in an attempt to suggest the outlines of this thinking about the risk that I regard as most pernicious: biological terrorism. It is written for those who desire a better understanding of this risk and its implications for policymakers. Section I delineates the problem that confronts us. It describes the character and magnitude of the risk of biological terrorism and identifies the factors that differentiate bioterrorism from other modes of terrorism. This section also comments on why biological terrorism has not yet emerged as an important instrument of terror and offers judgments about the likelihood of its manifestation over the next decade. Section II enumerates four factors that have confused, confounded, and constrained the U.S. response to this threat. Section III, the most operational part of this paper, offers my top 10 recommendations for moving ahead.