This article investigates factors that contributed to the successful introduction of 33 priority guidelines for Norwegian specialist health care from 2008 to 2012. The guidelines constituted an important step in changing the regulation of clinical priority setting from largely self-regulation by medical professionals to a more centralised and hierarchical form, and therefore, resistance from the medical profession was expected. My focus is on organisational factors within the project that developed the guidelines, using policy documents and project documents as the main source of data. I find that the project was characterised by a high level of autonomy in terms of how it was organised and the actors included, with significant capacity for action in terms of both structure and personnel, and a broad inclusion of affected actors. The priority guideline project was dominated by medical professionals, and its organisation did not represent a radical break with established traditions of medical professional self-regulation. Although organisational autonomy, action capacity and broad inclusion were clearly of importance, the project's compliance with historical traditions and norms of medical governance stands out as the key factor in understanding the successful establishment of the priority guidelines.