The main part of the water resources for the Algerian south provides for groundwater. This paper presents the various types of aquifers exploited in the area of the northern Algerian Sahara, as regards the problem of fluorine in particular. An outline of the concentrations and mineralisation of water are given, according to the various formations and/or geological structures, as well as food of the groundwater bodies. The presentation of the results obtained on the various groundwater bodies exploited in all the Eastern area of the septentrional Sahara, brings a reading as complete as possible of the chemistry of these water tables, for the drinking water supply as for the irrigation of the cultures. In fine the problems raised by the quality of this water are exposed, and various proposals to cure these problems respecting the public health.