According to a socio-ethnography of public action in progress, the article questions the conditions of deployment of a participation policy implemented by a Regional Health Agency (ARS) to develop its new PRAPS and the framing procedures chosen to govern the participation in its construction, its instrumentation and its logics of uses. On the basis of a documentary analysis and participant observations carried out within the participatory devices, considered as tools for legitimization and conduct of public action, we show that they are, on the one hand, strongly framed by procedures and formal rules elaborated by the ARS upstream and during the stages of construction of the PRAPS; on the other hand, as a contractual and incentive tools, they serve the logics of the participants contrasting uses that are likely to constrain and influence the ways of doing a relatively innovative and collective engineering for such an institution.
JEL Code: I18