Why are parent companies held liable for the infringements committed by their subsidiaries under EU competition law? This article examines the jurisprudence of the EU Courts with a view to illuminating the rationale underpinning parental liability. Taking a closer look at the �single economic unit/undertaking� explanation endorsed by the Courts post-Akzo, it demonstrates that this doctrine lacks the exegetical power assigned to it, insofar as it is based on a fallacious reasoning. With this in mind, two alternative justifications for parental liability are then discussed: the �failure to exercise vigilance� theory and the �enterprise� rationale. As the article illustrates, both justifications have their advantages and limitations. Ultimately, the final choice lies with the EU Courts, but it is submitted that, all things considered, the �failure to exercise vigilance� argument offers a better�or at least more realistic�solution to the problem of developing a coherent explanation for parental liability in EU competition law.