Abstract: Polychlorobiphenyls and other toxic halogenated polyaromatic substances such as various halogenated pesticides, herbicides, and the like, are dehalogenated through the use of a strong base and various sulfur-containing compounds. The dechlorinated residues either form polymers which are insoluble in aliphatic hydrocarbons and can thus be easily separated as through filtration, or can be separated from the solvent by distillation. The residues can be readily and safely disposed of as in an approved dump, or burned.