Public bioethics bodies are used internationally as institutions with the declared aims of facilitating societal debate and providing policy advice in certain areas of scientific inquiry raising questions of values and legitimate science. In the United States, bioethical experts in these institutions use the language of consensus building to justify and define the outcome of the enterprise. However, the implications of public bioethics at science-policy boundaries are underexamined. Political interest in such bodies continues while their influence on societal consensus, public (...) debate, and science policy remains ambiguous. This article presents a theoretical discussion of public bioethics bodies as boundary organizations and examines them in terms of relationship to the moral and cognitive authority of science and other forms of expertise, mechanisms for public participation in controversial science policy, and the deployment of consensus models. The theoretical discussion is examined in the case of the U.S. Human Embryo Research Panel. (shrink)