Tin dioxide nanotubes (200 nm in diameter) were synthesised by the sol-gel template method. The gas sensitivity of SnO2 nanotubes has been investigated. Due to the small grain size and large amount of grain boundary, SnO2 nanotubes demonstrated good sensitivity in sensing ethanol gas and had an ability to detect ammonia gas without any doping or surface modification. In2O3 semiconductor nanowires were synthesized efficiently by the chemical vapor deposition method through carbon thermal reduction. The diameter, length and morphologies of In2O3 nanowires can be varied by controlling the synthetic conditions. The In2O3 nanowires were characterised by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HRTEM). The application of In2O3 nanowires for gas sensors was tested.