Thermoplastic vulcanizates (TPVs) based on high impact polystyrene (HIPS)/styrene-butadiene rubber (SBR) blends were prepared by dynamic vulcanization technique. The rheological, mechanical and morphological properties of the dynamically vulcanized blends were investigated systematically. As determined by capillary rheometer, the apparent viscosity of the blends decreases as the shear rate increases, indicating obvious pseudoplastic behavior. At low shear rate, the apparent viscosity of these blends is considerably higher than that of neat HIPS and decreases with the increase of HIPS concentration. The increase of HIPS content in the dynamically vulcanized blends contributes to the increase of tensile strength and hardness properties, while elongation at break and tensile set at break reach a maximum at 30 and 50 wt % of the HIPS content, respectively. The etched surfaces of the HIPS/SBR TPVs were investigated using field-emission scanning electron microscopy, the morphological study reveals continuous HIPS phase and finely dispersed SBR elastomeric phase in the TPVs. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 2523-2529, 2010