This thesis is about public relations as an occupation and a business. The study is focused on investigating the nature of the expertise utilised in public relations, ways in which it is exploited commercially, and the consequences such practices have for the occupational group and its economic existence. The theoretical framework for this thesis combines insights from the sociology of the professions, studies of cultural/creative professions, Bourdieu's approach to the study of cultural practices, and critical examination of professional services, such as management consultancy. In empirical terms, the thesis combines a range of data and analytical approaches. The key part of the thesis is a model of public relations expertise derived from an analysis of participant observation of professional training. Its component parts are identified as: picture of the world; conceptual frame; and working knowledge, which in turn is composed of problems, tools and truths. The thesis also offers a narrative analysis of competition case studies, a particular genre of practitionars accounts of their own work, leading to the conclusion that their role is to show practitioners how to make sense of the immediate experience of work within a more abstract and ordered professional framework. A range of secondary data on the industry and the labour force are reanalysed to show how expertise is transformed into a commodity that can be priced and sold. The transformation involves an understanding of demand and supply dynamics for PR services. Finally, through the analysis of routine practices, the thesis draws attention to the occupation's "split personality" - two coexisting yet contradictory ways in which practitioners think about public relations - and pursues it at the level of the group's strategies designed to counteract the weaknessess resulting from this unsettled identity.