The environmental policy idea of sustainable development, of an economic system that safeguards the natural basis for life on this planet, requires that natural resources be used more economically. In view of the changes occurring in the earth’s climate, this means, in particular, reducing energy consumption. Discussions have been under way in Europe for some years now on rendering the use of natural resources more expensive by imposing taxes, e.g. on energy. The revenue derived from ecological taxes would enable existing taxes and social insurance contributions to be cut, mitigating their negative economic effects. The contributions to this volume examine the issue of an ecological tax reform from various angles. They provide scientific and ecological background information, put forward proposals for political implementation and report on current developments in France. The main contribution to this reader is a revised version of a study that has had a major impact on the political debate in Germany. In the study, which was commissioned by Greenpeace, the German Institute for Economic Research (DIW), Berlin, examined the economic effects of an ecological tax reform, taking as an example a tax on energy. The study shows that such a tax reform is economically acceptable and environmentally positive even if implemented in one 'pioneer' country alone. The ecological tax reform leads to a significant cut in energy consumption and does not pose a threat to German competitiveness.