Multi-wall carbon nanotubes were dispersed homogeneously throughout a poly( ether ether ketone) matrix by melt processing. The influence of nanotube content on both rheological and electrical properties was analysed. The dynamic storage modulus, G', shows a characteristic solid-like behavior above 1 wt% nanotubes. A sharp transition from an electrically insulating to a conductive composite was observed between 1 and 1.5 wt%. By applying a power-law relation, the rheological and electrical percolation thresholds were found to be 0.9 wt%, and 1.3 wt%, respectively. Considering this data, Guth's filler reinforcement theory provides a valuable estimation of the aspect ratio of the nanotubes after processing and indicates substantial length degradation during the dispersion process. (C) 2009 Elsevier B. V. All rights reserved.