This paper reviews the contribution the social sciences can make to the challenge of providing access to sustainable sanitation services and infrastructures for billions of people, in both the over- and underdeveloped parts of the world. The paper reviews and discusses three particular social scientific topics relevant for the sanitation challenge: the nature of socio-technical change, the issue of multilevel governance, and the role of the citizen-consumer. It is argued that sanitation is as much a social as it is a technical issue, and that the role of social scientific knowledge needs to be strengthened and given more attention in this context. The key contribution from the social sciences is to be found in its capacity to help widen the narrow, technical definitions of sanitation by including actors and their needs and belief systems, and by highlighting the alternative socio-technical tools and governance arrangements that are instrumental in moving beyond some of the dead-end roads of traditional water engineering and sanitation provisio