Neutron activation analysis was applied to seven water samples from selected geographical areas in the United States. The technique proved adequate for the identification and measurement of nineteen different elements ranging in concentrations from 0.00002 to 63.3 ppm. Irradiations were conducted in the Oak Ridge Graphite Reactor, gamma spectrometry serving as the principal tool for identification and measurement of specific induced radionuclides. The degree of chemical separation required for a given sample depended upon the element being determined and the variety of constituents present. It was possible to determine chlorine, sodium, and argon on the sample as irradiated. Most other elements required separation. Ion exchange and precipitation were investigated, and the latter proved most generally satisfactory. General chemical separation was adequate for certain elements. Others required specific procedures. A summary of the elements identified, time of irradiation, and analytical procedure is given. From the results reported it is believed that neutron activation analysis can be a valuable tool for sanitary engineers and geochemists in water studies. The techuique is specific in that each induced radionuclide decays with its own characteristic radiation and half life. It is sensitive in that concentrations as small as 10/sup -11/ gram of some elements canmore » be determined with an accuracy of 15% or better. The study reported was limited to elements yielding radionuclides with half lives ranging from minutes to days. Location of counting equipment nearer irradiation facilities would permit determinations involving radtonuclides of much shorter half lives, thus widening the range of elements suitable for analysis. (auth) « less