This article introduces a special symposium issue of the Antitrust Law Journal based on a conference on monopolization. It argues that monopolization law has been experiencing simultaneous expansion and contraction processes that are not wholly contradictory but at least partly complementary. Specifically, the authors suggest that the contraction of monopolization law in the United States and the EU might serve to facilitate its expansion and increased importance worldwide, providing other antitrust regimes with more focused and effective tools to address the challenges involved in regulating dominant firms. Moreover, monopolization law's increased reach internationally also has made its refinement and rationalization all the more important for jurisdictions seeking to avoid the harmful chilling effects associated with excessive enforcement in this area. Finally, the contraction of monopolization law might also be motivated by external pressures, resulting from spillover effects. A better understanding and evaluation of these expansion and contraction trends is therefore likely to necessitate their joint rather than separate evaluation in future antitrust scholarship.