This research investigates the fate and transport of methyl tert-butyl ether (MTBE) in phytoremediation, particularly the uptake and volatilization of MTBE in lab-scale hydroponic systems. The research reveals that MTBE was taken up by hybrid poplar cuttings and volatilized to the atmosphere. Volatilization of MTBE occurred through both stems and leaves. The concentration of MTBE in the transpiration stream declined exponentially with height, indicating that the uptake and volatilization along the stems are an important removal mechanism of MTBE in phytoremediation. Volatilization, via diffusion from the stems, has not been directly measured previously. No volatile MTBE metabolites were detected; however, mass balance closure and metabolite detection were not primary objectives of this study. The greatest amount of MTBE in plant biomass was associated with the woody stems from the previous year's growth, owing in part to the large biomass of stems. MTBE in the plant tissues appears to reach a steady state concentration and there does not appear to be an accumulation process that could lead to highly elevated concentrations relative to the groundwater source.