For futures studies and environmentalism the late 1960s and early 1970s were a heyday period of great publicity, and much scientific interest was devoted to them. The study 'Limits to Growth', commissioned by the Club of Rome, has played an important role for the further advancement of these fascinating fields. Each of them in its own way deals with the long term prospects of humankind and desirable future paths of humanity and the globe. This investigation illustrates a very important phase in the development of these two areas and writes a history of ideas and a history of impact of the Limits to Growth debate and other activities of the Club of Rome. It includes information that has so far only been known to a very limited number of directly involved individuals and looks into very recent stages of the sustainable development debate and newest developments of more pragmatic and critical futures studies. For the purpose of this study some 100 interviews have been made worldwide with very well known and often influential individuals. Among them are: Sicco Mansholt, Alexander King, Jan Tinbergen, Robert Jungk, Saburo Okita, Lord Kennet, Johan Galtung, Barry Commoner and Philip de Seynes.