Abstract This article analyzes how the concept of representativeness/representativity has been used by the European Union institutions to structure interest intermediation. It examines how the concept emerged and has been defined, and identifies its scope of application. Representativeness is mostly used to refer to organizational features of the interest groups (organizational representativeness), but is occasionally used in relation to representative aspects of the overall system of interest representation (system representativeness). The focus is primarily on aspects of descriptive representativeness– in particular, territorial and thematic representativeness – rather than on procedural representativeness that guarantees authorization and accountability. Originally applied to the social partners only, the White Paper on European Governance proposed to extend the use of representativeness to the wider category of civil society organizations. It will be shown that the application of the concept to these organizations proves more problematic than it does to the social partners. The European Transparency Initiative subsequently abandons representativeness, but it is argued that it contains the seeds for its re-emergence.