Unknown knowns-or "public secrets"-may play an integral part in publicly funded medical science. In one large transnational field research site in Africa, such unknowing pertains to vital material inequalities across the relations of scientific production. These inequalities are open to experience but remain often unacknowledged in public speech and scientific texts. This silence is not usually achieved by suppressing knowledge but through linguistic convention and differentiation between places and moments of knowing and ignorance. Switching between known and unknown according to situation and interlocutor is an important, largely implicit skill that maintains relations necessary to conduct clinical research-linking bodies, lives, institutions, and technologies across differentials of resources, expertise, and power. Unknowing, then, facilitates research; and it shapes the resulting work and perpetuates the political and economic contradictions that pervade the context and the research endeavor itself. Unknowing thus poses a challenge for conventional anthropological modes of critique and engagement. Unknown knowns-or "public secrets"-may play an integral part in publicly funded medical science. In one large transnational field research site in Africa, such unknowing pertains to vital material inequalities across the relations of scientific production. These inequalities are open to experience but remain often unacknowledged in public speech and scientific texts. © 2013 by the American Anthropological Association.