[Excerpt] The purpose of this chapter is to present a framework for the analysis of union coalition-building and demonstrate its utility using comparative empirical material mainly from the United States, Germany, and the United Kingdom though we also comment on union action in Italy and Spain. In what follows, we seek to define union-coalitions and specify their functions, identify a variety of types of coalition and the variety of factors that encourage unions to forge coalitions. We then set out and seek to explain the variable patterns of coalition use across our five countries. The chapter concludes in speculative vein, by considering the role that coalition building should and could play in the revitalization of national labour movements.