This discussion paper presents a review of the notion of Common But Differentiated Responsibilities (CBDR) in international negotiations. It thus aims to identify mechanisms that could contribute to reinvigorating CBDR as a meaningful guiding principle for a 2015 climate agreement under the UNFCCC. To this end, it first considers the normative framing of CBDR and reviews the way CBDR has been conceptualised and interpreted in the academic literature. Second, it scrutinises the way CBDR manifests itself under the UNFCCC and how it explains the Annex I / Non-Annex I dichotomy before it summarises the respective political standpoints of some of the UNFCCC’s most important and influential parties (or groups of states). Third, it provides an analysis of the way CBDR or CBDR-like approaches have been put into practice in a variety of international regimes and policy arenas, including the World Trade Organization, the Montreal Protocol and the burgeoning debate on universal Sustainable Development Goals.