The coliquefaction of chloroprene rubber (CR) and natural rubber (NR) was carried out at 300-420 degrees C with pressurized nitrogen gas and decalin as a solvent. Upon coliquefaction, ZnO in both NR and CR is expected to capture chlorine from CR. As a result, in comparison to the individual liquefactions of CR and NR, the increase of the captured amount of chlorine by zinc and the synergistic effects of the upgrading reaction, such as the increase of oil (hexane-soluble constituent) yield, were observed upon coliquefaction of CR and NR. These enhancements were not observed after the liquefaction of CR with ZnO addition. Therefore, it was considered that the temperature range of dispersion of ZnO from NR into the reactant was close to the temperature range of the formation of HCl from CR. Further, it was also anticipated that the stabilization of radicals from both CR and NR was enhanced by the coliquefaction. The alicyclic solvent, decalin, which swelled CR and NR very well, was the most suitable solvent upon coliquefaction. The effects of vulcanization and carbon-black additive in both CR and NR were negligible on coliquefaction.