A general synthetic method has been developed to fabricate and assemble ferromagnetic transition metal nanofibers. By employing the novel electrospinning technique followed by subsequent heat treatment, we have successfully prepared uniform nanofibers of Fe, Co, and Ni with diameters of similar to 25 nm and lengths longer than 100 mu m. Using a specially designed fiber collector, we can conveniently assemble magnetic nanofibers into aligned arrays. The electrospun magnetic metal nanofibers have unique magnetic properties, with much enhanced coercivities relative to bulk materials. The outstanding features of this approach to get one-dimensional magnetic nanostructure are its simplicity, effectiveness, and ease of assembly. Therefore, electrospun magnetic nanofibers can potentially be used in fabrication of high-density magnetic recording, magnetic sensors, flexible magnets, and spintronic devices.