Dielectric analysis IDEA) of molded ground waste rubber tire (GRT) and its chlorinated derivatives (Cl-GRT) was undertaken. Dielectric spectra of Cl-GRT show formation of a biphasic structure consisting of the rubbery phase and a hard phase whose relaxation occurs in the high-temperature region. DEA of plasticized poly(vinyl chloride) (PVC) containing GRT and PVC containing Cl-GRT was also undertaken. It is observed that PVC containing Cl-GRT exhibits a higher loss factor in the high-temperature region than does the PVC compound containing GRT, due to enhanced interaction between Cl-GRT and PVC. While the activation energy for dielectric relaxation of PVC does not change when compounded with GRT, it does decrease when PVC is compounded with Cl-GRT due to dipolar interaction.