The use of proliferation of nanotechnology in commercial applications is driving requirements for minimal chemical processing and simple processes in industry. Carbon nanofiber (CNF) products possess very high purity levels without the need of purification processing before use and are in growing demand for this quality. Polyetherimide (PEI) has excellent mechanical and thermal performance, but its high viscosity makes its nanocomposites processing very challenging. In this study, a facile melt-mixing method was used to fabricate PEI nanocomposites with as received and physically treated CNFs. The dispersion of CNFs was characterized by scanning electron microscopy, transmitted optical microscopy, and electrometer with large-area electrodes. The results showed that the facile and powerful melt-mixing method is effective in homogeneously dispersing CNFs in the PEI matrix. The flexural and tribological characteristics were investigated and the formation of spatial networks of CNFs and weak interfacial bonding were considered as competitive factors to enhanced flexural properties. The composites with 1.0 wt% CNFs showed flexural strength and toughness increased by more than 50 and 550%, respectively, but showed very high wear rate comparable with that of pure PEI. The length of the CNFs also exerted great influences on both mechanical and tribological behaviors. POLYM. ENG. SCI., 50:1914-1922, 2010. (C) 2010 Society of Plastics Engineers