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Water crises are already stressing societies, economies, and the environment worldwide and especially developing countries. The expected growth in population, urbanization and economic activity, as well as the impact of climate change, will exacerbate the situation in the coming decade. In developed countries, conventional water supply and wastewater disposal systems ensure safe access to drinking water, sanitation and wastewater services. The worldwide application of conventional systems is, however, only possible to a limited extent. The reason for this is that these systems are designed for certain climatic conditions and also do not consider the varying requirements regarding water supply and wastewater disposal typical for developing countries. Although there are alternative water supply and wastewater disposal systems that have proved to be successful throughout the developing world, there are still several barriers to their worldwide adoption. To increase the establishment of these approaches this paper focuses on aspects of particular relevance for developing countries, namely: water reuse (untreated wastewater), alternative sewerage (settled and simplified sewerage), alternative wastewater treatment (waste stabilization ponds, constructed wetlands and up-flow anaerobic sludge blanket reactors) and management of water losses (real and apparent losses).