The fact that antitrust infringements, in particular hard-core cartels, cause significant harm is widely acknowledged. The Court of Justice of the European Union (CJ) confirmed the horizontal direct effect of EU antitrust provisions in damages actions before national courts with the seminal judgments in Courage and Manfredi. However, due to various technical, economic and legal difficulties experienced by claimants, private enforcement of competition law remains underdeveloped resulting in billions of euros of damages that are foregone annually. Adopted with the aim to help victims of antitrust infringements to obtain full compensation, the Damages Directive provides a set of minimum requirements to be implemented into national law. According to EU law, interest constitutes an essential component in making good the damage sustained and should be due from the occurrence of the harm until full compensation is paid. Interest is calculated in accordance with national law provided that the EU principles of equivalence and effectiveness are complied with. National provisions on interest are often drafted for the case of contractual debts, not for tort claims resulting from long-lasting clandestine infringements such as, for instance, cartels. The absence of specific guidance on the relevant scope of the EU acquis on interest brings additional difficulties in conforming interpretation of national law by judges or the amendment thereof by national legislators. This leads systematically to situations where the adequate amount of interest is not claimed or granted. As a result, victims are deprived, at least partially, from an essential component of their right to full compensation.