Legislation aiming at establishing a media system and the application of these laws follows the constitutional lawcriteria of plurality and diversity.However, no available objective standard exists that would allow us to declare whether these criteria are indeed met or not. By way of contrast, both legislators and enforcers of the law are repeatedly required to evaluate the diversity of the media system. In the ambit of several national jurisdictions a concentration of undertakings engaged on the media market is subject not only to a thorough competitive assessment but, also, to an authorisation to be provided according to regulatory provisions that fall under the scope ofMedia law. Under this scope, it is therefore assessed with the involvement of the media authority in the competition law processes whether and to what extent pluralism of media supply is impeded by the concentration in question. This study summarises the experiences with respect to the assessment of media plurality from the perspective of those enforcing the law.