Large-scale arrays of feather-like boron nanowires have been successfully prepared using magnetron sputtering with a target of highly pure boron and boron oxide mixture. The morphology, microstructure and composition of the feather-like boron nanowires are characterized in detail using scanning electron microscopy, transmission electron microscopy, and electron energy-loss spectroscopy. Elemental mapping has been used to investigate the distribution of boron and oxygen in the boron nanowires. It is revealed that the feather-like boron nanowires possess the microstructure of outer oxidized coating layer and inner pure boron. The thickness of the outer oxidized layer is about 1-2 nm. Our results may provide opportunities to understand the fundamentals of boron chemistry and to fabricate new nanodevices. (C) 2002 Elsevier Science B.V. All rights reserved.