An analytical method has been developed for concentrating, extracting, separating, and identifying natural organic compounds present in sub parts-per-million quantities in potable water. The developed technology consists of extracting trace organic compounds from water by means of macro-reticular resins, eluting them by simple and rapid solvent methods, separating the mixtures by gas chromotography, and identifying and quantifying the various pollutants by combination gas chromotography mass spectometry. The experimental XAD-2 method was compared to the standard EPA approved solvent extraction method for determining chlorinated pesticides in water and showed it to be more effective, even at parts-per-trillion levels, in recovering dieldren from river water. More than 150 compounds were identified (in about half of these cases even the specific isomer was identified) in the raw and/or treated water from fifteen Iowa and Nebraska communities.