Ultrasound assisted twin screw extrusion process was developed to disperse carbon nanofibers (CNFs) in a polymer matrix. CNFs were separately added into the melt stage to reduce the breakage of CNFs and to avoid intense stresses in the feed zone. The effect of ultrasound and CNFs loading on die pressure, rheological, mechanical, electrical and morphological properties of liquid crystalline polymer (LCP) filled with 0-20 wt% CNFs was studied. Ultrasonic treatment caused a reduction in die pressure and a decrease in electrical percolation threshold value of treated samples. It was also found that mechanical properties of ultrasonically treated LCP/CNF nanocomposite moldings were preserved, improved or slightly decreased in comparison with those of LCP. This is in contrast to available literature typically showing a deterioration of mechanical properties with addition of CNFs. SEM studies have indicated an improved dispersion of CNFs and a reduction of LCP rich area in nanocomposites upon ultrasonic treatment. (C) 2010 Elsevier Ltd. All rights reserved.