Polystyrene (PS)/polyamide 1212 (PA 1212) blends were compatibilized with a maleated triblock copolymer of styrene-(ethylene-co-butene)-styrene (SEBS-g-MA). Scanning electron microscopy revealed that the addition of SEBS-g-MA was beneficial to the dispersion of PA 1212 in the PS matrix because of the reaction between them. The variation of the fraction of SEBS-g-MA in the blends allowed the manipulation of the phase structure, which first formed a sheetlike structure and then formed a cocontinuous phase containing PA 1212/SEBS-g-MA core-shell morphologies. As a result, the mechanical properties, especially the Charpy notched impact resistance, were significantly improved with the addition of SEBS-g-MA. Differential scanning calorimetry (DSC) data indicated that the strong interaction between SEBS-g-MA and PA 1212 in the blends retarded the crystallization of PA 1212. The heat distortion temperature of the compatibilized blends was improved in comparison with that of the unmodified blend, probably because of the apparent increase in the glass-transition temperature with an increasing concentration of SEBS-g-MA. (C) 2005 Wiley Periodicals, Inc.