The effect of retorting, i.e., combined temperature and high relative humidity conditions, on the morphology, structure, and thermal characteristics of a number of extruded films containing binary and ternary blends of a 32 mol % ethylene-vinyl alcohol copolymer (EVOH) with amorphous polyamide (aPA) and nylon-containing ionomer as blending additives was carried out. Each film was investigated by differential scanning calorimetry, attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and synchrotron X-ray scattering. The oxygen transmission rate of multilayer structures having as barrier element the cited blends was also measured and the results were interpreted in terms of the blends' particular structural and morphological features. From the results it was found that the thermal properties, the crystalline structure, and the water resistance of the blends were improved upon retorting compared with neat EVOH. However, only the binary blend with aPA showed a real enhancement in the oxygen barrier properties immediately after retorting compared with neat EVOH. This unprecedented and surprising effect was additionally ascribed to the retorting-induced compatibilization between EVOH and aPA components of the blend as determined by SEM. (C) 2008 Wiley Periodicals, Inc.