By the end of the Clinton administration, the claim that terrorists armed with biological weapons represented a huge threat to the security of the United States had achieved the status of received knowledge. How this linkage was forged, despite informed dissent not only outside the Clinton administration but also within it, and how it was used to justify a radical reframing of biological knowledge, especially in genetic engineering and genomics, in terms of military goals is the subject of this essay. My method is historical. I assume that no category is fixed but, rather, that key terms, such as "weapons of mass destruction," "biological weapon," and "terrorism" itself, are contingent, shaped under specific historical and political circumstances, and are therefore more fluid than often thought. This account draws on a wide variety of sources including government documents, policy papers and books, conference records, media materials, memoirs, and detailed interviews with nine subjects selected from among participants in the events examined. It shows that the nature of a linkage between terrorism and biological weaponry was debated at many levels in Washington, and it offers reasons why, ultimately, a counterbioterrorism "bandwagon" was constructed and began rolling at the end of the second Clinton administration.