The concept of eco-industrial sites or sustainable business sites is a noteworthy newcomer in the family of location types. The origin of this type may be considered as a consequence of two development trends, namely the segmentation of the location market on the one hand (an outcome of changing locational tendencies) and the aim of government policy to integrate economic and environmental objectives on the other. In this paper, both trends are analysed. The central aim is to establish the progress of implementing the newly developed location concept in practice and to identify factors of success and failure. The situation in the Netherlands is used as a frame of reference. After the outline of the background, the concept of sustainable business sites, including its definition, is considered and criticized. Then a tentative inventory is presented of the approximately 60 eco-parks which have developed in the past 10 years in the Netherlands, including the results of a questionnaire survey of these 60 parks. To get a better insight into the factors which determine success or failure, short case-studies of a number of the parks are presented. Finally, a number of conclusions are presented, including a discussion of an alternative view of the concept of eco-industrial sites which applies to the continuity of both firm and environment.