Electrospinning is a method to produce polymer fibers from solution (or melt) with diameters ranging from 100 to 500 nm. A thermoplastic polyurethane was electrospun from solution to produce an isotropic fiber mat. The mechanical behavior of the mat was characterized by uniaxial tensile tests. The electrospun polyurethane produces a stress-strain response characteristically different to that of the material from which the mat is spun. Scanning electron microscopy and infrared spectroscopy were also used to characterize the electrospun material and determine the source of the differing mechanical responses. (C) 2003 Elsevier Ltd. All rights reserved.