Accounts of the development of partnering in construction often stress the importance of formal mechanisms for ‘engineering’ collaboration and underplay the impact of social dynamics on the development of the relationship. Drawing upon case study evidence from two very different partnering projects, this paper examines the ways in which the nature and quality of relationships between client and contractor depend upon a complex and dynamic interplay of formal integrative mechanisms and informal social processes. The paper draws out a number of key implications for understanding partnering in practice. First, that attributing project success (or failure) to partnering is by no means a straightforward exercise. Second, that there is no one strategy or template for effective partnering. Third, that partnering is a dynamic process, involving short-term learning and mutual adjustment. Fourth, that wider organisational structures and cultures often have an impact upon partnering relationships. Finally, that partnering does not necessarily resolve project problems at source.