Edible oil was injected at five sites to promote reductive dechlorination. The edible oil was injected as a non-aqueous phase liquid (NAPL) or as an emulsion of oil, an emulsifier, and water. At Dover Air Force Base, injection of the emulsion into a barrier resulted in greater distribution of the total organic carbon (TOC) and more rapid dechlorination than direct injection of the edible oil into another barrier. Direct addition of oil using a GeoprobeÔ direct push rig promoted reductive dechlorination in two sites with shallow groundwater contamination. The emulsion moved at least 7.6 m at a site on Long Island, NY. An increase in the intermediate and final degradation products ethene and ethane was noted over the first four months after injection. The emulsion was distributed throughout a 7.6 m zone surrounding the four injection wells in a deep aquifer at Edwards Air Force Base. Little dechlorination has been observed at this site after two months. Direct oil injection is generally less expensive when the contamination is shallow and site conditions allow rapid installation of GeoprobeÔ points. Injection of the oil-in-water emulsion is more cost effective when the contamination is deeper or where a larger area must be treated. However, injection of the emulsion requires an additional handling step and a suitable water supply, but results in a superior product that can be readily introduced into the subsurface.