Rule of reason, passing-on defence, per se infringements, extraterritoriality, illegally obtained evidence, alternative explanations, indirect evidence are only some of the notions interpreted and applied by competition law courts on both sides of the Atlantic. Do the judges analyse and apply them in a similar fashion? Given that two courts of the same jurisdiction may hold differing views on the same issue, one might say that the question is not worth asking. But still. The question is worth asking when various jurisdictions are compared, each one taken as a whole, with a focus on the substance rather than on differing formulas. This special issue brings together a critical mass of articles enabling the practitioner to gain an overview of complex matters in a concise but also precise way.