Via vaporization of Fe and Si powders mixed with a molar ratio of 1:1, alpha-FeSi2 nanowires were synthesized on one Si wafer, where the temperature is higher than 950 degrees C and Fe supply is enough, and meantime Si nanowires were obtained on the other Si wafer, where the temperature is lower than 500 degrees C and Fe atoms are much less than Si atoms in vapor. The two kinds of nanowires have diameters of 40-80nm and lengths of 3-10 mu m. Their shapes, crystallinity, and compositions are studied in terms of field emission scanning electron microscopy, X-ray diffraction spectra, and energy dispersive X-ray spectroscopy. From the obtained experimental results, we explain the growth mechanism of the two kinds of nanowires using the vapor-liquid-solid growth model. Two important conditions, high temperatures and enough Fe supply, are emphasized for syntheses of the alpha-FeSi2 nanowires. (c) 2005 Elsevier B.V. All rights reserved.