There is tremendous current interest in transporting DNA molecules through nanopores. This interest stems from the possibility of using nanopores for characterization/sequencing, separation, and sensing of DNA. In the presence of a transmembrane electric field, typically used in such applications, DNA chains can be driven through the nanopore via the electrokinetic transport processes of electrophoresis and electroosmotic flow, as well as by diffusion. To our knowledge there have been no quantitative studies of the relative importance of the electrokinetic and diffusive components for DNA transport in a nanopore system. We describe such quantitative studies here. We report on the transport of a series of single-stranded homo-oligonucleotides made of thymidine bases through nanopores in a polycarbonate filter membrane. We show that when an ionic current is passed through the nanopores, transmembrane DNA electrophoresis is the dominant transport process. Finally, the pores in these membranes have conical constrictions at both membrane faces. The effect of this interesting pore geometry on DNA transport is also discussed. (C) 2003 Elsevier Ltd. All rights reserved.