"Who's Agenda?: The paper will consider the variety of processes by which knowledge about sustainable development is becoming a field of professional expertise in a number of European countries. It will point to the paradox that sustainable development is thought to require participation in decision making by consumers and users of the built environment, not private, professional knowledge. The impact of Non Governmental Organizations: Although the established professions are claiming ownership of much of the expertise required, and are often supported by government in these claims, an important factor, identified by anthropologists such as Douglas and Wildavsky, is that the environmental movement has been largely generated by non governmental and hence anti- professional, because anti-establishment, organizations.Interviews and Case studies: The paper will explore these issues with reference to interviews undertaken with founders of the movement in a number of European countries, and some of their "followers" who are putting the ideas into practice. It will show how their contributions interact in a number of case study sustainable development projects.Partial non-professionalisation: The evidence suggests that there are a variety of ways in which this type of knowledge is being created and then put into practice. It is being adopted as "conventional wisdom", but continues to be contested, as there are always alternative formulations which could have been adopted and alternative organizations who could have claimed ownership of the knowledge concerned. Sustainable development expertise is, and is likely to remain, the most political of professionalisms, and thus the most insecure. "