Specialist and lay ethical expertise in public health: issues and challenges for discourse ethics In recent decades, both public health professionals and the populations targeted by prevention and health promotion programs have shown an increasing interest in ethical issues since some interventions have been seen as impinging on fundamental rights and values. Insofar as bioethics is not adapted to population interventions and community health issues, a specific expertise in public health ethics is now required. However, ethical expertise in this area faces many challenges. The purpose of this paper is to examine four of these challenges. The first three challenges concern professional or specialist expertise. The paper suggests that expertise in public health ethics should go beyond the search for greater sophistication in defining ethical principles. Experts in public health ethics also need to identify appropriate strategies to include public health professionals in ethical analysis and to adopt a critical and reflexive approach to the status of moral experts and moral expertise. However, the main challenge is to identify appropriate ways of reconciling lay and specialist ethical expertise. The paper argues that secular morality and common morality represent two key sources of lay ethics expertise and that the fundamental values that inform discourse ethics should be derived from both forms of expertise