In the context of the recent transformation of control in Swedish health care, the changing role of quality registers are analysed as a vivid example of how professional groups become involved in new modes of regulating professional work. Based on a critical appraisal of the main currents in the research on NPM, it is argued that understanding the productive side of power is an underexploited theme. The main part of the article is devoted to a detailed analysis of how a seemingly insignificant, but in its consequences important, professional practice was transformed from a resource for clinical research, an entirely professional concern, to a tool for hierarchical control. In the concluding sections, a number of important conditions for the successful use of soft power in modern societies are identified and discussed.