The nonisothermal crystallization behavior of syndiotactic polystyrene (SPS)/ atactic polystyrene (APS) blends was studied with differential scanning calorimetry to investigate the effects of APS on the crystallization behavior of SPS. Polarized optical microscopy and wide-angle X-ray diffractometry were also used to observe the morphology of the SPS crystalline structure. From a cyclic heating/cooling temperature program, we obtained found that APS retarded the crystallization (and recrystallization) of SPS and made the crystal less perfect, but the ultimate crystallinity of SPS did not change with the addition of APS. We also observed that APS was disposed in the interfibrillar region of SPS spherulites and did not change the crystalline form of SPS. This result will be helpful for improving SPS applications through blending with rubber-toughened APS. (C) 2000 John Wiley & Sons, Inc.