Price and quota agreements in the context of so-called hardcore cartels typically cause damages due to excessive prices at downstream firm level. In recent years, these ‘private’ damages gained importance in competitive policy. Damages claims brought forward against former hardcore cartel members are seen as a further element in the fight against hardcore cartels. Against this background, the project in a first step develops a theoretical framework for the calculation of damages caused by hardcore cartels. In a second step, the developed framework is applied to data of actual cartel cases. Based on the gained insights, a set of principles for a sustainable determination of damages is derived that takes the existing law provisions explicitly into account.