Tungsten oxide (WO3) nanocrystalline powder was successfully synthesized by direct precipitation technique starting from sodium tungstate dehydrate (Na2WO4 center dot 2H(2)O) as precursor at 80 degrees C for 48 h. The morphological characteristics, distribution, and crystallite size of WO3 nanocrystalline powder were analysed by transmission electron microscopy, X-ray diffraction, and the Fourier transform infrared spectroscopy. According to transmission electron microscopy results, the mean particle size of WO3 nanocrystalline powder was approximately determined as 41.7 nm. The gas sensing performance of WO3 nanocrystalline powder for saturated toluene vapor was measured by two probe resistivity unit in a closed vessel at room temperature. In addition, WO3 nanocrystalline powder was able to respond the lowest concentration of 500 ppm. The results showed that the sample exhibited high sensitivity (93%) and good response reproducibility (0.93 + 5.5%) for toluene vapor.