International audienceThis paper presents and puts into perspective the five articles that make up the thematic issue “Trade unions facing public sector transformations”. It recalls the contingent nature of the boundaries between public and private worlds of work. It shows that public sector trade unions are adjusting their strategies and practices in response to profoundly changed conditions and that this adjustment takes the form of an hybridization in which some new features, imported from the private sector, are adopted in a way and on a scale that vary from situation to situation. After showing that these changes are part of a longer-term historical process and that the relations between state and trade unions in the public sector are ...