The humidification-dehumidification process (HD) is an interesting technique adapted for water desalination when the demand is decentralized. This technique presents several advantages such as flexibility in capacity, moderate installation and operating costs, simplicity, possibility of using low temperature energy (geothermal, solar, recovered energy or cogeneration), etc. Although the common methods of desalination such as distillation and reverse osmosis are the subject of many investigations (archived data and principle of function validated), studies of the HD process are limited at the laboratory step or patents. The aim of this paper is to present the principle of functioning and the characteristics of this technique. The state of the art concerning the HD technique is presented. Several installations functioning worldwide with the HD technique are presented, analyzed and evaluated: solar and geothermal desalination units, a plant functioning by mechanical compression of humid air and an installation functioning by absorbing water from the humid atmosphere. Finally the perspectives of the HD process are evaluated and discussed.