Doctor of Philosophy / An organisation’s knowledge base is a valuable asset that serves as a source of sustainable competitive advantage for the firm. Organisations have become increasingly reliant on the application of knowledge work and the contributions of professionals to the creation of valued organisational knowledge. Implicitly, the literature has assumed permanency in the employment relationship between professionals and organisations and focused on issues such as organisational identification and commitment, and extra-role behaviours of professionals as impacting on their knowledge sharing behaviours. However, the nature of professional or expert employment has become more transient. There has been a marked increase in the use of professionals in contractual roles where the association with the organisation is often temporary and contingent. But the organisational implications of such practices remain largely unexplored. In particular, there is a dearth of research examining the impact of contract professionals on knowledge flows within the firm and on their motivations to participate in knowledge sharing within organisations. This dissertation addresses this gap in the literature. This study examines the knowledge sharing practices of contract professionals in contemporary organisations. Conceptualising knowledge as socially situated and constructed, this qualitative study examines professionals employed as contractors in two large organisations: a large bank and an insurance company; and, based on in-depth semi-structured interviews with contractors and managers, considers why and how professionals engaged as contractors choose to share what they know with the contracting organisation. Engaging with research literatures from knowledge management, professional identity, newer career forms, and psychological contracts, the study generates a typology of contract professionals that suggest distinct knowledge sharing orientations. The study constructs three categories of contractors: Free Agents, Specialists and Consultants, identifies factors that influence and inhibit the knowledge sharing motivations of these categories of contractors and provides recommendations for a more holistic knowledge management strategy for organisations utilising contract professionals. The findings from this doctoral research show how identity work can have practical implications for knowledge management. For example, by exploring the dynamics of professional identity and image construction, the research shows how identity and image influences both the contractor’s knowledge sharing behaviours and the organisation’s knowledge management strategies. Exploring new areas of professional contingent work, this research aims to make a significant contribution to the understanding of knowledge sharing, professional identity and the management of contract professionals within organisations.