The carbon nanofibers used in this work were derived from polyacrylonitrile/N,N-dimethyl formamide precursor solution using electrospinning and vacuum pyrolysis techniques. Their conductivity sigma was measured at temperatures between 1.9 and 300 K and transverse magnetic field between -9 and 9 T. Zero magnetic field conductivity sigma(0, T) was found to increase monotonically with the temperature with a convex sigma(0, T) vs T curve. The conductivity increases with the external transverse magnetic field, revealing negative magnetoresistance at temperatures between 1.9 and 10 K, with a maximum magnetoresistance of -75% at 1.9 K and 9 T. The magnetic field dependence of the conductivity can be explained using the two-dimensional (213) weak localization effect. The temperature dependence of sigma(0, T) can be explained using a modified simple two-band model with temperature-dependent carrier mobility, and a correction introduced by 2D weak localization. (C) 2003 American Institute of Physics.