This special issue is concerned with knowledge sharing and boundary crossing. Knowledge management is a constantly expanding field. Like any research area, it is shot through with complex questions. This is certainly the case with regard to boundaries, since they constitute both a bounding line that has to be crossed if the knowledge required for innovation is to be diffused and a form of protection for scientific and technological organisations and institutions. The studies published in this special issue clearly illustrate this complexity, since they are concerned with processes such as learning, the dynamic of expertise, the joint creation of knowledge, the resource-based view, brokering activities, HRM (Human Resources Management) processes and the dynamic of scientific disciplines. The objects under investigation are very diverse; they include project teams, luxury hotels, urban projects, hospitals, clusters, the aeronautics industry and agricultural systems. These studies draw on approaches that have become established over time. There is a history behind the succession of approaches in the field of knowledge management (Snowden, 2002),so it may be useful to put these various pieces of research into context. The central question of this special issue is that of boundaries: between projects, between organisations, between types of knowledge, between scientific disciplines and, of course, between actors. This examination of boundaries leads to a state of the art review that begins with the question of knowledge transfer. Van Wijk & al. (2008) consider the antecedents of the transfer considering three major topics: knowledge, organizational and network characteristics. We take adifferent approachusing ahistorical approach to theconcepts. Following Tsoukas (1996, 2009), we propose to criticize the dominant approach of the transfer. In addition, we want to show and comment the change from the concept of knowledge transfer to the concept of boundary. In a constructivist way (Le Moigne, 1994, Von Glasersfeld, 1995) and with Holford (2015) we propose the concept of boundary construction in order to underline the role of interactions " actors-objects-actors " .