In the present article, we describe an experimental study of blends of polycarbonate (PC) with acrylonitrile-butadiene-styrene graft copolymer (ABS) melt mixed in two types of single screw (varying in compression ratio) and twin screw (counter and co-rotational) extruders. The effect of screw design variation is qualified via storage and loss moduli differences obtained for particular screw geometries. Rotational rheometer with parallel-plates geometry was used to determine dynamic viscoelastic properties at a strain of 1% selected as the value representative of the linear viscoelasticity. Measurements were carried out at 220, 240, and 260 degrees C and angular frequencies in the range from 0.1 to 100 rad/s. Regardless of the dependences variation with blend compositions, mixing performed on the extruder with counter rotating twin screws resulted in the lowest viscoelastic response in the whole range investigated. The theological observations were confirmed by the results of SEM analysis. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 2847-2853, 2010