A sanitation system is much more than a technology. It encompasses the collection, transport, treatment and management of the end products of human excreta, solid waste, industrial wastewater and storm water. Sanitation systems can be regarded as sustainable if they protect and promote human health, do not contribute to environmental degradation or depletion of the resource base, and are technically and institutionally appropriate, economically viable and socially acceptable. It is not always simple to identify the sanitation solution that complies with this definition of sustainability. This paper outlines a strategy for achieving this goal on a project level.