Model bioblends were investigated for interfacial adhesion using the asymmetric double cantilever beam (ADCB) fracture method. The model bioblends comprised two synthetic polymer components, one of which was the nonbiodegradable polymer polystyrene (PS). The second component was a synthetic biodegradable polyester, which was either polycaprolactone (PCL) or Eastar Bio Copolyester(R) (EBU). The critical strain energy release rate (G(lc)) data from the ADCB fracture experiments on the model bioblends decreased in the order: PCL/PS > EBU/PS. This was opposite to the reported order in the interfacial tension of these bioblends. It is concluded that the relative interfacial adhesion of the model bioblends was due to better compatibility in PCL/PS blends over that in EBU/PS blends. (C) 2004 Wiley Periodicals, Inc.