The first part of Architecture of Development Assistance is devoted to the 2011 DAC Report on Multilateral Aid. These key messages provide an overview of recent trends in multilateral aid and how countries decide between multilateral and bilateral aid. The overriding trend is one of decline in aid volumes after the historic high of 2009, but the picture in reality is more complex depending on whether aid is earmarked or not. The overview also considers the five big groupings of multilateral organisations that account for the vast majority of aid and discusses non-DAC donor multilateral aid. Finally, it considers the case for multilateralism, and looks at examples of countries’ multilateral aid decisions and the evidence they are built upon.