Abstract: Polychlorinated biphenyls are chemically degraded by contact with a Lewis acid catalyst in a nonaqueous liquid medium, in the presence of a cation which combines the chlorines on the PCBs to form a solid chloride of the cation which will precipitate out from the liquid medium. Preferred Lewis acids are metal halides, particularly a combination of aluminum chloride and ferric chloride, and the preferred cation is potassium in the form of potassium hydroxide. The process is susceptible to both batch and continuous operation. The process for chemically degrading PCBs with a Lewis acid catalyst can be applied to PCB-containing soils, sediments and sludges by contacting those materials, under anhydrous conditions, with Lewis acids and preferably with Lewis acids and a metal cation capable of reacting with the hydrohalogen released from the PCBs by the Lewis acids. The Lewis acids may be supplied to the process by the adventitious corrosion of a vessel containing the PCB-contaminated soil.