Poverty and attendant sickness are often extreme in the rural Third World, demanding special awareness and effort in their alleviation. The approaches to water supply covered here are also extreme to match, in the sense that they deal with water recovery in arid regions using minimal resources; they deal with treatment of highly contaminated water, and they deal with distribution at its minimum level. Outside of many developing countries, the conditions of water supply are likely to be less difficult, so these techniques could be built on and modified to meet requirements. This paper is not intended as a field worker's manual, but as an introduction to the problems of Third World development, the concept on appropriate technology plus the role it can play in development, and to the application of this concept to the specific requirements of small-scale drinking water supply.