This research program was initiated with the overall objective of developing a practical method for the concentration of trace amounts of organic compounds in water for use in biological testing. The principle behind the isolation-fractionation scheme developed in this program is to separate dissolved organics into fractions by adsorption onto different adsorbants (i.e., XAD-8 resin, AG MP-50 cation exchange resin, and graphitized carbon (black) under varying pH conditions. Twenty-two model organic compounds covering a broad spectrum of chemical classes, functional groups and molecular weights were used to monitor process performance. Lab-scale experiments, were performed in an effort to determine optimum conditions for the final pilot-scale evaluation of the isolation-fractionation scheme. The amounts of each model compound in each fraction were monitored using GC/MS procedures that were developed specifically for this program. Recoveries ranging from 30 to 90% were obtained for fifteen of the twenty-two compounds. The results of the pilot-scale study utilizing five 100-liter test solutions spiked with model compounds at microgram/L concentrations confirmed those of the lab-scale studies.