The UN human rights treaty bodies are still in need of reform, since past initiatives were not as successful as hoped. Therefore, to secure the effective dischargement of their various mandates, particularly under the reporting procedure, the Committees need to be reformers on their own. Nils-Hendrik Grohmann delineates the Committees' powers from both a practical and theoretical perspective and demonstrates how far their legal mandates can reach. Effectiveness-orientated interpretation of procedural provisions that already endow the Committees with certain powers, allows for the extension of mandates. Thereby, the Committees can introduce new powers without State consent. In doing so, they are well-advised to approach the reporting procedure holistically, to develop coherent procedural approaches and to take into consideration the considerable overlap in terms of substantive provisions under the nine UN human rights treaties. Another key factor for reform is cooperation itself among the Committees, which increased in recent years through the Meeting of Chairpersons.