Traditional studies of long-term change in trade union structure have predominantly focused on aggregate trends in union merger activity in constructing explanations of change. Using the Australian trade union movement as an example, this article argues that our understanding of the long-term change in the external structure of trade unions would be better served by a structural events approach (Waddington, 1995) that examines the incidence of union formations, dissolutions, and breakaways, in addition to that of union mergers. In doing so, this article presents new data on structural change in the Australian trade union movement between 1986 and 1996, and explains the additional contribution made by union dissolutions and union formations to the reductionist effects of the merger wave that dominated these years.