The term «promotion» as applied to research has long been reserved to «hard» science in the sense of «economic valorisation». With the prevalence of project-based research, where sponsors expect a return on investment over and above the publication of specialised articles, «societal» promotion, more broadly defined to include HSS and once less visible, has since come of age. This dossier, which is first and foremost a forum of opinion, presents a collection of contrasting views and lessons learned about a practice which adopts highly varying forms (dissemination of knowledge, scientific mediation, transfer of know-how to communities, patents, etc.) and is becoming increasingly professionalised. What is at issue is the difficulty of popularising, of adapting and adjusting the message to suit the target audience, of relations between researchers and their promoters, of the importance of showing «how science is done» and not simply what it produces, and of «political time», which is not the same as research time.