Describes a method for recovering trans-1,2-dichloroethene from a liquid feed composition comprising both the cis-and trans-isomers of 1,2-dichloroethene and contaminating amounts of other chlorinated hydrocarbons, e.g., lower alkyl chlorinated hydrocarbons, such as C.sub.1-C.sub.2 chlorinated hydrocarbons. In one of the described methods, the liquid feed composition is introduced into a first distillation column 10 wherein the stereoisomers and chlorinated hydrocarbons more volatile than the stereoisomers are removed as overhead 12 and charged to a second distillation column 20. In column 20, the stereoisomers are separated from the more volatile chlorinated hydrocarbons, and a bottoms fraction 24 comprising the stereoisomers is charged to a reactive distillation column 30 wherein the cis-isomer is isomerized to the trans-isomer in the liquid phase and in the presence of an organic free-radical initiator, e.g., an azonitrile initiator. Substantially pure trans 1,2-dichloroethene is recovered as overhead 32 from reactive distillation column 30.