Electrospinning was used to make activated carbon nanofibers with polyacrylonitrile (PAN) as the precursor. The applied voltage was found to be more influential on electrospun PAN fiber diameters than the flow rate and needle tip-collector distance. Tensile load and tear strength of electrospun PAN membranes increased with thickness, accompanied with a decrease in air permeability; however, burst strength was not significantly influenced by the thickness. Electrospun PAN nanofiber membranes were stabilized in air and then activated at 800 degrees C with KOH as the activating agent to make activated carbon nanofibers. Stabilized PAN membranes showed different breaking behaviors from those before stabilization. The maximum tensile stress of the stabilized PAN membranes from different concentrations was affected differently by the stabilization process. The resulting activated carbon nanofibers had no C N bond. The activation process generated micropores which contributed to a large surface area of 936.2 m(2)/g and a micropore volume of 0.59 cc/g. Pore size distributions of electrospun PAN and activated carbon nanofibers were analyzed based on the Dubinin-Astakhov equation and the generalized Halsey equation. The results showed that activated carbon nanofibers had many more micropores than electrospun PAN, increasing their potential applications in adsorption.