This book examines sequential coalition formation in oligopolies. Coalitions refer to mergers and acquisitions, cartels, and associations. The principal aim is the prediction and explanation of the coalition structure - whether an industry will emerge as a monopoly, say, or as a collection of sub-coalitions. In environments where decisions to form coalitions are made sequentially, the prediction and explanation of the equilibrium coalition structure can differ dramatically from the textbook simultaneous-move model. This difference derives from the knowledge effect, which is unique to the sequential-move models.