SnO(2) nanowires with lengths in the tens of micrometres range have been synthesized on a large scale via a facile polyethylene glycol-directed method at ambient temperature followed by a suitable thermal treatment of the precursor nanowires. The morphology of the precursor of the SnO(2) nanowires is tunable by changing the concentration of either SnCl(2) or polyethylene glycol. After calcination, the resulting SnO(2) nanowires retain a similar shape to the precursor, but with hierarchical architecture, which can be considered as one-dimensional nanowires assembled by interconnected SnO(2) nanoparticles with a high surface-to-volume ratio. The SnO(2) nanowires are investigated with XRD, SEM, TEM, and gas sensing tests for detecting CO and H(2). It is found that the present SnO(2) nanowires exhibit a remarkable sensitivity and low detection limit (10 ppm for H(2)), as well as good reproducibility and short response/recovery times, which benefit from the unique hierarchical structure with a high surface-to-volume ratio and the 3D network formed by the nanowires.