The principles, values and manifestations of multilateralism, including the United Nations, are under sustained scrutiny and assault. Their performance and effectiveness are questioned, as are their decision-making procedures and their representation according to modern standards of accountability and democracy. All this has a corrosive effect on their legitimacy. This publication explores the performance and future of multilateral approaches and institutions with reference to major global challenges such as international security, terrorism, HIV/AIDS, environmental sustainability, economic justice, human rights and humanitarian assistance.