International organizations (IOs) matter. This book uncovers the regular working world of IOs, examining whether, to what extent, and how these 'global governing bodies' can act independently of the will of states. This book explores this issue by asking who or what shapes their decisions; how and when decisions are made; how players interact within an IO; and how the interactions vary across IOs. The Working World of International Organizations examines three working groups in the higher echelons of IOs - state representatives, as proxy of states, serving in the Executive Boards or General Councils, chief officers of IOs, and the staff of the permanent secretariat. The book demonstrates that none of them are unified; in each there are contested ideas about strategy and appropriate projects, and analyses their interactions to explain who is able to shape or influence decisions. Six representative IOs are studied to identify the relevant critical determinants that shape the behaviour of players. The volume explores how these players have an impact over three dilemmas that are common to all IOs: priority and agenda setting, financing, and the centralization or decentralization of operations.