Nanofibrous membranes offer unique properties for filtration- and adsorption-based separations including high specific surface area, good interconnectivity of pores and the potential to incorporate active chemistry on a nanoscale. The most versatile process for producing a nanofibrous membrane is electrospinning. Electrospinning process parameters such as the applied electric field (drawing rate), the rotational speed of collector (collection rate) and the tip-to-target distance strongly influence the extent of fiber crossing that occurs while collecting the nanofibers and affect the fiber arrangements. In turn, they have an effect on structural and transport properties of the electrospun mat. We investigated the structural and transport properties of electrospun membrane in relation to the processing parameters in order to understand the distribution, deposition and orientation of nanofibers in the nanofibrous filtering media. Our results demonstrate that control over the pore size distribution can be achieved by coordinating the drawing and collection rates. (c) 2006 Elsevier B.V. All rights reserved.