This book analyses the transnationalisation of collective bargaining by European trade unions, presenting key theoretical concepts and debates on the Europeanisation of collective bargaining and social dialogue. The author uses comprehensive empirical evidence to illustrate that trade union strategies can be linked to sector-specific economic, institutional and actorrelated factors. Looking at seven different industrial sectors, the book investigates whether western European trade unions pursue a centralised, vertical approach towards the transnationalisation of collective bargaining policies or embark upon decentralised, horizontal cross-border initiatives. It identifies and operationalises the most important determinants of processes and explores commonly held assumptions about relationships between different forms of trade union-driven transnationalisation. Overall, the study reveals a number of patterns in the variation between countries and sectors, both of the institutions and instruments involved and of the intensity of cross-border coordination.