The miscibility and thermal degradation of blends of poly(bisphenol A carbonate) (PBC) with poly(vinyl chloride) (PVC) have been studied in inert atmosphere by a differential thermal/thermogravimetry analyzer. The blend showed a single glass transition temperature consistent with the Fox equation prediction suggesting the complete miscibility of the polymers. In the degradation of binary blend, PVC is stabilized slightly while PBC is destabilized significantly. Fourier transform infrared studies of the blend showed the presence of chlorine even after the dehydrochlorination stage. Thus, chlorine radicals or hydrogen chloride formed during the dehydrochlorination of PVC migrates and abstracts hydrogen from the PBC leading to the destabilization. The degradation of polymers with various metal oxides such as ZnO, Fe 2O3, Co3O4, and TiO2 and metal chlorides such as AlCl3, ZnCl2, FeCl3, and CoCl2 was studied. Experimental data indicate that the increased degradation of the polymer blend in the presence of metal oxides is due to the formation of metal chlorides during the dehydrochlorination of PVC. These results indicate the high reactivity of chlorine radical or hydrogen chloride formed leading to the destabilization of polymers.