The thermal degradation of blends of PVC with bisphenol A polycarbonate has been studied by thermogravimetry and thermal volatilisation analysis. In the TG experiments, both programmed heating and isothermal heating (at 280-degrees-C) were used and the full composition range from PVC to polycarbonate was examined. In the TVA experiments, blends of equal weights of the polymers were employed and the volatile and tar/wax fractions of products were both studied. As initial separation of the volatile product fraction by subambient TVA was used to assist product identification, which was based on IR and MS methods. In the degradation of the blends, the PVC is slightly stabilised, but there is a considerable destabilisation of the polycarbonate. The latter phenomenon has been explained in terms of a reduction in molecular weight in the temperature region in which dehydrochlorination is occurring due to migration of chlorine radicals from the PVC phase to the polycarbonate phase, where hydrogen abstraction from methyl groups in the polycarbonate is believed to occur.