The tensile and impact resistance of impact-modified poly(ethylene terephthalate) (PET) is investigated. The impact modifiers are polyolefin-based elastomers or elastomer blends containing glycidyl methacrylate moieties to improve the adhesion with the polyester. The tensile properties are measured on injection molded specimens at room temperature while the Izod impact strength is measured from -40 to 20degreesC. The blend morphology is observed by scanning electron microscopy and the dispersed phase average diameter is determined by image analysis. The relation between the impact resistance and the phase morphology is discussed, and the critical ligament size for PET is determined. (C) 2003 Wiley Periodicals, Inc.