Nanosize fibers were fabricated using an extra-cylindrical electrode connected with single and multiple nozzles of an electrospinning process to stabilize the initial spun jets. To predict stability of spun jets, an electric field concentration factor (EFCF), which could be defined as a degree of a convergence of jets to a spinning axis, was introduced. The proposed parameter EFCF is utilized for the comparison of the experimental results for single and multi-nozzles electrospinning process. To consider the mass productivity of the multi-nozzles electrospinning supported by an auxiliary electrode, the weight of nanofibers that were spun to a rectangular shape target plate during 40 min was measured. The result indicates that the modified electrospinning technique shows a possibility as a useful method for increasing the production rate of nanofiber manufacturing. (c) 2006 Elsevier Ltd. All rights reserved.