Aliphatic diesters of unsaturated aliphatic C.sub.10-30 dicarboxylic acids are low temperature plasticizers for PVC. PVC is plasticized by contacting it with a plasticizing effective amount of an aliphatic diester of an unsaturated aliphatic C.sub.10-30 dicarboxylic acid wherein the aliphatic portion of the diester is a saturated or unsaturated, linear or branched, cyclic or acyclic unsubstituted or hydroxy-substituted aliphatic radical having from one to 10 carbon atoms.