In this chapter we examine the origins, nature and practical implications of the idea of “community of practice”. We argue that the concept has been used both to illuminate the challenges of creating a “learning culture” in health care and to establish initiatives promote knowledge transfer and sharing. After clarifying some of the key concepts under discussion, the chapter illustrates the general features of this broad family of interventions, discusses their characteristics and summarizes their key success factors. It also shows how the ideas of community of practice and situated learning have been applied in diverse ways by health care organizations and funders, how theses ways of knowing and learning have been inserted into the established institutional order, and the mixed, but sometimes promising, outcomes which have flowed from them.