In order to study the effect of introducing ethylene-ethylacrylate copolymer (EEA) in carbon black-HDPE composite systems, two HDPE-EEA composites prepared by pre-blending and masterbatch-blending processes were compared with HDPE and EEA composites in terms of positive temperature coefficient (PTC) characteristics and percolation threshold. The percolation threshold of masterbatch-blended composites occurred at the lowest carbon black concentration among four kinds of composites. The conduction path in the masterbatch-blended composite is effectively formed as a result of the localization of carbon black distribution predominantly in the EEA phase, resulting in an increase of conductivity. I-peak values, the resistivity ratio of the peak to 25 degrees C, of two blend composites were lower than those of HDPE composites. The I,, values, the resistivity ratio of 85 degrees C to 25 degrees C, of masterbatch-blended composites were higher than those of pre-blended as well as HDPE composites. It is evident that since most carbon black is dispersed in the EEA phase of the masterbatch-blended composites, the conduction networks are mainly broken by the crystal melting of EEA before the temperature reaches the crystal melting temperature of HDPE.