The miscibility of poly(vinyl chloride) (PVC) and a biodegradable aliphatic-aromatic copolyester (AAC) was investigated by differential scanning calorimetry. The thermooxidative degradation of the blends was investigated thermogravimetrically. The blends were prepared by dissolution in 1,2-dichloroethane and precipitation with methanol. The investigated blends were completely miscible with the glass-transition temperatures best predicted by the Fox equation. Fourier transform infrared analysis showed that the interactions responsible for miscibility were the hydrogen bonds between the blend components. The thermooxidative stability of the PVC/AAC blends was improved compared to that of pure PVC. Furthermore, when AAC was added, the dehydrochlorination rate of PVC decreased, and the maximum rate shifted to a higher temperature. (c) 2006 Wiley Periodicals, Inc.