Triethylene glycol (TEG), diethylene glycol (DEG), and ethylene glycol (EG) are commonly used to dehydrate the natural gas stream. These compounds may be introduced into the sub-surface environment as a result of spills, leaks, mechanical failures, and past disposal practices. The toxicity of the dehydration glycols at concentrations typically found in the subsurface in the vicinity of a dehydration unit is generally considered to be low. However, the miscibility of the glycols suggests that they may act as cosolvents for other more toxic, less soluble, organic compounds such as polycyclic aromatic hydrocarbons (PAHs), thereby increasing the subsurface mobility of those compounds. In 1998, a series of laboratory-based research activities was initiated to determine 1) the nature of cocontaminants that may be associated with the gas dehydration process, particularly spent glycols, 2) the biodegradability of the dehyradation glycols under environmentally relevant conditions in soils from three different gas-producing regions of North America, and 3) the potential effect of the dehydration glycols on the subsurface mobility of PAHs in the same three North American soils.