The analysis of Australian union behaviour, growth and structure has centred on the relationship between unions and arbitration. To varying degrees it has been assumed that Australian unions are dependent on arbitration for the supply of resources critical to their functions. The nature and extent of this dependency have, however, remained empirically unexplored. Yet it is clear that if this dependency relationship were a valid description of the relationship between unions and arbitration, its implications for the survial of unions under a different labour law regime would be profound. This paper, through the investigation of four historical case studies. questions the validity of the dependency hypothesis as a useful explanation of Australian union behaviour. A number of concerns emerge from the case analysis. To begin with, the general interpretation of key historical moments that the dependency hypothesis relies on does not capture the diversity of experience evident in these four cases. While arbitration played an important role in influencing union behaviour by altering the costs and incentives of pursuing particular strategies, the evidence suggests that a range of other factors account for this diversity. Moreover, arbitration was not only an institutional structure that unions faced. Rather, part of their strategic interplay with it was concerned with shaping the system to further their own goals through the use of different 'bundles' of political and industrial resources at the disposal of individual unions. Most importantly, to the extent that these unions were dependent organizations, they were dependent on a range of institutional and organizational mechanisms for the supply of critical resources. Arguably, this study also has profound implications for how more generalized accounts of union development are constructed and theorized. A localized analysis, which focuses on individual unions and their own microcontexts, is advanced as a more appropriate starting point for union theory.