The purpose of this paper is to present the known facts relating to Tertiary aquifers of the San Juan Basin in New Mexico. These facts are based on data collected from observations at outcrop" correlations of electric logs, data of pumping test, of water wells and chemical analyses of water samples. Some of these rocks have the basic characteristics of aquifers and are composed of clastic sediments that are porous, permeable and contain water. Not all tertiary clastics of the San Juan Basin are aquifers. Some beds are porous and permeable, but do not contain water. Whereas other beds are porous and contain water, but are not permeable. The rocks which cannot yield water in quantities and at rates sufficient for use are the silts, clays and sandy shales.