In this letter, we report on a technique for the hierarchical assembly of nanofibers into crossbar nanostructures. An electrospinning process is used to create polymer-based nanofibers with diameters ranging from 10-180 nm and lengths of up to several centimeters. By controlling the electrostatic field and the polymer rheology, the nanofibers can be assembled into parallel periodic arrays. We also propose a theoretical model for the process. (C) 2003 American Institute of Physics.