If we take a long-range view of competition regimes, we can document in the 20th century a case of major transformation.There has been a double evolution – away from cooperation and cartelization and towards competition on the one hand, from nationally bounded regimes to a globally interconnected regulatory sphere on the other. The antitrust tradition that emerged in the USA at the turn of the 20th century has gained significant and widespread influence after 1945, imposing itself in many parts of the world. The objective of this article is to retrace the process by which antitrust has gone from being a local legal rule to a nearly global structuring frame.We trace the fate of a local set of ideas turning into international politics and globally accepted principles. We also show that those global principles are subject to and interact with local politics - through the process of diffusion but also in their implementation.