The fate of selected volatile organic compounds (VOCs) in anoxic or anaerobic selectors was investigated at pilot scale. Tetrachloroethylene, 1,4-dichlorobenzene, and 1,3,5-trimethylbenzene were consistently removed at efficiencies in excess of 30%. The removals observed in this study were highly compound specific. Compounds with similar chemical structures such as toluene and 1,3,5-trimethylbenzene displayed substantially different behavior. The selector biomass concentration and hydraulic retention time were found to have little apparent effect on the VOC removal efficiencies. However, the results were confounded by a change in wastewater temperature that also influenced the loading of nitrate on the selector. The results of these experiments demonstrate the potential of selector technologies for reducing the mass loading of VOCs to aeration basins. The lower mass loadings should reduce the mass of aerobically recalcitrant VOCs that will be stripped to the atmosphere. Water Environ. Res.,67, 798 (1995).