The renewed interest in 'public sociology' has sparked debate and discussion about forms of sociological work and their relationship to the State and civil society. Medical sociologists are accustomed to engaging with a range of publics and audiences inside and outside universities and are in a position to make an informed contribution to this debate. This paper describes how some of the debates about sociological work are played out through a 'health impact assessment' of a proposed housing renewal in a former coal mining community. We explore the dynamics of the health impact assessment process and relate it to wider debates, current in the social sciences, on the 'new knowledge spaces' within which contentious public issues are now being discussed, and the nature of different forms of expertise. The role of the 'public sociologist' in mediating the relationships between the accounts and interpretations of lay participants and the published 'evidence' is described as a process of mutual learning between publics, professionals and social scientists. It is argued that the continued existence and development of any meaningful 'professional sociology' requires an openness to a 'public sociology' which recognises and responds to new spaces of knowledge production.