Building on the contribution of practice perspectives in highlighting the social construction of knowledge, it is proposed that additional insights can be gained by considering knowledge as a local discursive achievement and knowing as discursively performed. HR provides a particularly germane context for this exploration. While a growing volume of research problematises HRM, literature regarding HR professionals remains broadly functionalist. It emphasises the roles necessary to successfully deliver HRM; roles achieved through the application of specialist professional knowledge. In contrast, here HR professionals' work and identity is regarded as emergent, requiring continual negotiation and validation of their knowledge, both within the broader framework of HRM and the specific organizational context. From this perspective, examining knowledge as a local discursive achievement offers the opportunity of critical insight into HR professionals' practice. These ideas are explored through an ethnographic study of a HR department which had recently undergone substantial organizational change. HR professionals' construction and negotiation of, and indeed competition for, knowledge are examined as they attempt to secure professional legitimacy in the aftermath of this change. Through a discourse analysis of observational, interview and documentary data, a range of knowledge claims are examined. The analysis considers how personal knowledge and experience are positioned as the most credible sources for identifying solutions to HR problems. These problems are embodied in employees and therefore 'knowing people' becomes an essential aspect of knowledge claims. The invocation of experience involves relative (I know more) rather than absolute (I know about) claims which further provide a (not uncontested) means of dividing HR work according to hierarchical seniority. Through considering the dynamic nature of these constructions and their relationship to the subject positions enacted (including knower and known) this analysis extends both our understanding of HR professionals' practice and the social construction of knowledge