This paper considers the roles and definitions of expert and lay members of ethics committees, focussing on those given by the National Research Ethics Service which is mandated to review all research conducted in National Health Service settings in the United Kingdom. It questions the absence of a specified position for the ‘professional ethicist’ and suggests that such individuals will often be lay members of ethics committees, their participation being a reflection of their academic interest and expertise. The absence of (...) a specified position for professional ethicists and the concomitant but implicit denial of ethical expertise appear to be an anomalous state of affairs if one considers that the training offered to members of ethics committees is often delivered by academic ethicists. It is suggested that this is based on a misunderstanding of the concept ‘ethical expertise’ and that properly understood the ethicist can assist the work of ethics committees by drawing on their expert knowledge. (shrink)