Blends of poly(butylene terephthalate) (PBT) with poly(acrylonitrile-butyl acrylate-styrene) (ABAS) were characterized by differential scanning calorimetry, infrared, thermogravimetric analysis, and wide-angle x-ray diffraction (WAXD) studies. Addition of ABAS polymer to PBT improved the thermal stability of PBT. Infrared studies showed that ABAS polymer chemically interacts with PBT. The crystallization behavior of PBT was modified in the presence of ABAS polymer. The ABAS polymer showed inappreciable effect on melting behavior of PBT but decreased its crystallization. WAXD studies showed some modification in PBT peaks and a peak with increasing intensity corresponding to the P-crystalline form of PBT. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1657-1663,2009