This chapter aims to show the endurance of United Nations Conference on Trade and Development (UNCTAD) as the source of heterodox ideas about trade and development. It traces the life of these ideas and shows that while they have enduring purchase, they are ultimately mediated by the power dynamics inherent in the multilateral trade regime. The chapter also highlights the limited effects of UNCTAD-sourced ideas and policies, the historical failure of special and differential treatment (SDT) and policy space to achieve meaningful development opportunities, and the continued ability of the rich world to shape the global trade agenda. It reflects upon the enduring relevance of UNCTAD in light of these challenges. Over the past 30 years, the principles of non-reciprocity, SDT, preferential market access, policy space for development, and special categorisations for developing-country sub-groupings have diffused from UNCTAD to the GATT/WTO and have become ubiquitous in the multilateral trading system.