Poly(butylene terephthalate) (PBT)/talc composites were prepared through a single-screw extruder in the absence or presence of ultrasonic irradiation. A special exit die, which could be regarded as a capillary, was attached to the extruder to measure the effect of ultrasound on the melting temperature and pressure. The experimental results show that with the introduction of ultrasound and with its increasing intensity, the processability of the composites was improved. The morphology of the composites was also investigated by scanning electron microscopy. It was shown that ultrasonic oscillations improved the dispersion of talc in PBT and, furthermore, increased the crystallinity of PBT. Therefore, the mechanical properties were promoted through ultrasonic extrusion but decreased once the ultrasonic intensity was higher than 200 (or 150) W. This deterioration of the mechanical properties was induced by the ultrasonic degradation of PBT. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 2708-2714, 2011