This report deals with the determinants and success factors underlying institutional mergers, in particular mergers of private companies, government agencies and public sector entities. Within these three types of consolidations, we note that the objectives are linked to economic efficiency gains, the implementation of a specific strategy or policy and the deployment of resources in a simpler or more effective way. A literature review confirms that the success of a merger will firstly depend on an organization's ability and willingness to quantify, measure and track anticipated economic efficiency gains. The results will then be dependent on the internal expertise and the political influence which was instrumentalized within the framework of the merger. Finally, they will depend on the nature and the flexibility of the resources and capabilities which vary according to the culture of the organizations, and play an important role in the context of the transformations studied. In order to promote the chances of success of mergers, regardless of the sector, two elements seem essential and inseparable: excellent mutual knowledge of the entities involved and an ambitious, detailed integration plan with measurable milestones.