Eco-villages: Eco-villages are experimental places for sustainable building and sustainable living. The Netherlands are developing there first eco-villages, near the new-town Almere. In this paper we discuss the position of eco-villages within a sustainable development. We emphasise on the more difficult part; the role of eco-villages within social sustainability.Two case studies: In this paper we use two case-studies; the Farm, U.S.A. and ECU-village, The Netherlands. Both quit different, but with the same goal. The research consists of participation, interviews and observations. In this paper we discus the common ground of both projects.The Farm: The Farm is a sustainable community with a history of 30 years. The social interaction within the community has contributed to sustainable development. The latest effort is there involvement in a global academy for sustainable building. At the same time: the Farm also includes elements of a social cage. The community has an open minded attitude, but thus not includes strangers easily.ECU-village: This is a new project for sustainable living in The Netherlands. It’s also like the Farm a holistic (and maybe, hippy-based) community. This village likes to be autarkic in an environmental sense, but will fulfill a cultural function within Almere. This also leads to a dualistic image; something between a social cage and a cultural attraction.Conclusions: Eco-villages contribute to a sustainable development; by reducing environmental impact and as an example of a sustainable lifestyle. This example’s are not to be copied one to one, but need interpretation. The form of social interaction within the village is depending on the relations with the outside world. A strong local network works can be durable, if it is combined with a lager social network. This can be the social context of the villages, but also a global network. If an eco-village becomes a social cage, it isn’t durable. Within this context, the built environment places also a role in facilitating social interaction.