Focusing on PP which is readily subject to thermo-oxidation, and PBT which is highly resistant to thermo-oxidation, methods for evaluating the degradation of resin were studied by comparing the chemiluminescence with conventional general evaluation methods. In the case of PBT, only the slope method of the line approximation was an effective anal. method for chemiluminescence although the results did not demonstrate a stable trend. As for general methods, as previously reported, the MMB quantity by the reaction thermal decomposition GC/MS method was the best followed by the peroxide value measuring method in second place. In the case of PP, on the other hand,all anal. methods other than the slope method of the linear approximation were effective for the chemiluminescence, and it was confirmed that all general methods are also effective. The stage where chemiluminescence occurs in the degradation reaction mechanism was examined This is bimol. termination reaction of peroxide radicals or when the peroxide radical was split into hydroxyl radicals and macro-alkoxy radicals in the case of PBT. However, it was assumed that chemiluminescence occurs when high heat is generated due to the bimol. reaction of hydroperoxides in the case of PR It had been proposed that chemiluminescence is an effective evaluation method at the beginning of degradation This was not true for all resin types. In the case of PBT the correlation was not recognized at all while the retention of the number average mol. weight lowered to 80% or with mileage of the vehicle collected from the used cars. But,the correlation with emission intensity was established for PP even when the number average mol. weight decreased by less than half. The same result was also obtained for PVC wire insulators. Therefore, it was clarified that suitability for evaluation of degradation due to chemiluminescence varies greatly depending on the resin type. In addition, it can be said that black materials are not appropriate because black pigments absorb chemiluminescence.