"Ethics" is used as a label for a new kind of expertise in the field of science and technology. At the same time, it is not clear what ethical expertise consists in and what its political status in modern democracies can be. Starting from the "participatory turn" in recent social research and policy, we will argue that bioethical reasoning has to include public views of and attitudes towards biomedicine. We will sketch the outlines of a bioethical conception of "public understanding of ethics," addressing three different issues: (a) the methodological relevance of moral questions and problems raised by lay persons in everyday life regarding biomedicine and technology, (b) the normative relevance of such lay moralities for the justification of ethical decisions, and (c) the necessity of public deliberation in this context. Finally, we draw conclusions in view of the concepts and methods such a conception of "public understanding of ethics" should employ.