The global environmental governance architecture is set to undergo major reforms, with the main decisions on reform to be taken at the June 2012 Rio+20 UN Conference on Sustainable Development. Discussions on reform have focused on whether the United Nations Environment Programme (UNEP) should retain its institutional status as a subsidiary body of the UN General Assembly, or be transformed into a specialized agency—a World Environment Organization—of the UN. The choice of institutional form, however, cannot be made without reference to both the needs of global environmental governance, and the factors impeding the effectiveness of the current governance architecture. This article takes a historical perspective, highlighting the similarity between the current debate on institutional form, function and financing; and the choices that the original designers of the governance architecture made 40 years ago. The fundamental global environmental problems and the functions of effective global environmental governance, though evolving, have remained largely unchanged. The historical reasons for creating UNEP as it is currently formed thus remain valid today, and provide useful analytical input to the current debate. This article further argues that the reasons for UNEP's shortcomings have little inherent connection to its institutional form, and cannot be resolved simply by a change in status. Deeper, yet probably easier to accomplish, reforms should focus on enabling UNEP to fulfill its intended role as an effective anchor institution for the global environmental governance architecture.