Mechanical properties, flow characteristics and chemical resistance of polycarbonate (PC)/poly(butylene terephthalate) (PBT)/impact modifier (IM) blends were investigated over the wide composition range of PC and PBT Mechanical properties of the PC/PBR/IM blends for two different IMs, butadiene based IM and butyl acrylate based IM, were studied. For the study of chemical resistance of the PC/PBT/IM blends, test specimens were dipped in solvent, thinner and then variations of mechanical properties were analyzed. Tensile and flexural strengths were increased linearly and heat distortion temperature (HDT) also increased as PC content in the blends increased. Impact strength increased drastically as PC content in the blends increased up to 50 wt. - %, and then it leveled out for over 50 wt. - % of PC. Flowability of the blends decreased as PC content increased. Impact strengths of the blends were different from IMs specially at low temperatures. The blends with butyl acrylate based IM showed slightly higher impact strength than the blends with butadiene based IM at 0degreesC and room temperature. However the blends with butadiene based IM showed remarkably higher impact strength than the blends with butyl acrylate based IM at the temperatures below 0degreesC. After the chemical treatment of test specimens, tensile and flexural strengths decreased, and impact strength increased as PC content in the blends increased. PC in the blends would become mild and ductile when it contacted with solvent, thus the impact strength increased while tensile and flexural strengths decreased.