Blends of poly(vinyl chloride) (PVC) and biodegradable aliphatic-aromatic copolyester (AAC) were prepared, and their physical, thermal, and mechanical properties were studied. Biodegradation in the presence of the lipases of Rhisopus arrhisus or Candida cilindracea was monitored as well. The physical properties of the blends, such as density and softening temperature, were between those of each component. Differential scanning calorimetry measurements showed that the blend components were completely amorphous and miscible. Obviously, PVC suppressed the crystallization of the partially crystalline copolyester. AAC was the thermally more stable component, and it seemed to improve the thermooxidative stability of PVC in the blends. The lipases of R. arrhisus and C. cilindracea no doubt catalyzed the ester hydrolysis of AAC, although the PVC matrix limited the rate and extent of the hydrolysis. (C) 2008 Wiley Periodicals, Inc.