Three types of carbon nanofibers (MJ, Pyrograf (R) III PR-19 and PR-24) were incorporated into linear low density polyethylene (LLDPE) using intensive mixing. The electrical volume resistivity of composites decreased with the addition of CNFs from over 10(12) Omega cm for pure LLDPE to less than 10(4) Omega cm for carbon nanofibers (CNF) contents of 15 wt% or more. Tensile modulus increased from 110 MPa for pure LLDPE to 200 MPa and 300 MPa for 15 wt% MJ and 15 wt% PR composites, respectively. However, the tensile strength remained fairly unchanged at about 20 MPa. Strain-to-failure decreased from 690% for pure LLDPE to 460% and 120% for 15 wt% MJ and 15 wt% PR composites, respectively. It was inferred that the interfacial interactions of LLDPE matrix with MJ fibers is better than that with PR fibers, resulting from the rougher surface of MJ fibers. POLYM. ENG. SCL, 50:93-99, 2010. (C) 2009 Society of Plastics Engineers