High electrically conductive composites have been manufactured using twin and single screw extruders from carbon black with polyolefin. High density, low density polyethylene, polypropylene, polyethylene/polypropylene copolymer, and maleic anhydrite grafted polypropylene have been compounded with three carbon blacks (CBs), i.e., Black Pearl, Printex, and Ketjen, respectively. The lowest percolation threshold (0.8 vol%) for conductive composite was obtained using Ketjen CB blended with high density polyethylene (HD3690, MFI = 36 g/10 min). Polypropylene composites also achieved low percolation thresholds of 1.5 vol % when compounded with Printex or Ketjen CB. Decreasing melt viscosity of polymer matrix resulted in decreasing resistivity of composites. Ketjen CB showed the best conductive behavior for both polyethylene and polypropylene composites. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 3527-3534, 2010