Saline water is arbitrarily defined as water containing more than 1000 milligrams per liter of dissolved solids. Saline ground water is known to underlie about two‐thirds of the 48 states. Locally, aquifers yield saline ground water in profuse quantities, some of which is used by industry, particularly for cooling. Generally, however, saline water has been considered a nuisance. In this report it is dealt with as a resource, especially for the future. Forty chemical types of mineralized ground water were recognized, but sodium chloride dominates the occurrences and is almost the only type found where concentrations exceed about 20,000 mg/l. The occurrence and hydrologic properties of saline water aquifers deserve much more study than they have had.