Communicating science in public involves multiple asymmetries: of knowledge, power, role, and trust. These asymmetries often create conflict, and in the late twentieth century they eroded public confidence in expertise and institutions. The loss of public confidence provoked an institutional response, the development of the new discipline of risk communication. This earlier period of rhetorical change in the relations between science and its publics offers perspective on the issues raised by the recent cases examined in this volume. This essay reviews the history of risk communication in light of these issues.