This study explains the history and politics of dam building worldwide and shows why large dams have become so controversial. It details the ecological and human impacts of large dams and shows how the national interest argument is used to legitimize uneconomic and unjust projects which benefit elites while impoverishing others. The technical, safety and economics problems of dam technology are described, along with the structure of the international dam-building industry, and the role played by international banks and aid agencies. The book goes on to tell the story of the rapid growth of the international anti-dam movement, and some of the most important anti-dam campaigns from around the world. It then shows how the dam lobby and governments have reacted to criticism by cosmetic greening of the dam-building process, and through state repression. Alternatives to dams are then put forward, with the argument that their replacement by less destructive alternative requires the opening up of the industry's practices to public scrutiny.