This work focuses on the development of electrically conducting porous nanocomposite structures by the incorporation of multiwalled carbon nanotubes (MWNT) into electrospun poly(ethylene oxide) (PEO) nanofibers. Electron microscopy confirmed the presence of individual aligned MWNT encapsulated within the fibers and showed fiber morphologies with diameters of 100-200 nm. Electrical conductance measurements of the random nanofiber mats showed that by increasing the concentration of MWNT we were able to produce porous nanocomposite structures with dramatically improved electrical conductivity. Above a percolation threshold of 0.365 +/- 0.09 MWNT weight percent (wt %) in PEO the conductance increased by a factor of 10(12) and then became approximately constant as the concentration of MWNT was further increased. Because of this percolation threshold, for a 1 wt % loading of MWNT, the conductivity is essentially maximized. Mechanical testing confirmed that the tensile strength did not change, and there was a 3-fold increase in the Young's modulus when comparing a 1 wt % MWNT loading to the pure electrospun PEO. Thus, the optimal MWNT concentration for PEO nanofiber mats with enhanced mechanical and electrical properties is similar to 1 wt %.