The history of institutional change in the European Union shows that its motivations and dynamics vary widely over time. It is nevertheless possible to identify three permanent factors of change, whose respective weight varies, and to identify the conditions under which they may influence the negotiations. In the history of the EU, a substantial number of Intergovernmental Conferences (IGCs) have taken place, five of which were held between 1986 and 2000. Gradually a certain tradition for setting up IGCs has emerged, one that encompasses procedural rules and norms as well as informal and established practices. It was argued that a proper analysis of treaty reform processes in the EU requires a dynamic perspective on decision-making, going beyond the individual IGC as a moment of formal treaty reform. The decision-making process needs to be situated in a distinct historical, institutional, and contextual setting, revealing how actors are embedded in a web of structuring elements.