Development assistance has for many decades been aiming to support developing countries’ strategies to achieve more sustainable development. Yet, evidence shows that the impact of such assistance has been well below expectations. This study examines the efforts of assistance providers and recipients to enhance the effectiveness of development assistance, particularly during the first 15 years of this century. Triggered mainly by two United Nations conferences in 2000 and 2002, which launched the Millennium Development Goals and addressed development financing issues, respectively, a series of High Level Forums were organised by the Organisation for Economic Co-operation and Development to consult periodically on how to improve development assistance effectiveness. The study analyses the evolution of commitments made and actions taken to achieve this goal, identifying progress and challenges, and capturing the broadening of the debate, its participants, and the emerging, more complex global setting of development cooperation. Prominent among recent changes was the negotiation of an accord to launch the Global Partnership for Effective Development Cooperation, in Busan in December 2011. The latter part of the study looks into the structure, modalities and actions of the Partnership and concludes with a critique of its record to date and an assessment of its future prospects.