The world's largest commodity traders have a significant impact on the modern agri-food system. Archer Daniels Midland (ADM), Bunge, Cargill and Louis Dreyfus, are dominant traders of grain globally and central to the food system, but their role is poorly understood. This report considers the traders - collectively known as the ABCDs - in relation to several global issues pressing on agriculture: the 'financialization' of both commodity trade and agricultural production; the emergence of global competitors to the ABCDs; and some implications of large-scale industrial biofuels, a sector in which the ABCDs are closely involved. The report includes a discussion of how smallholders in developing countries are affected by these changes, and highlights some development policy implications. The report highlights the ways in which these four firms are decisive actors in the global restructuring of the overlapping food, feed, and fuel complexes that is now under way, and considers how the firms are evolving as they respond to and shape new pressures and opportunities in the food system.