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In this paper supersensitive gas sensors incorporating single SnO 2 -nanowires integrated on Si for the detection of gases relevant to environmental and safety issues are presented. The SnO 2 -nanowires are produced by a spray pyrolysis process followed by subsequent tempering, which results in growth of single-crystalline SnO 2 -nanowires with diameters of 30 -250 nm and lengths up to several 100 µm. TEM-analysis reveal the single crystalline character of SnO 2 -nanowires with two preferred growth directions. The nanowires are removed from their substrate and transferred to another Si-substrate coated with 750 nm SiO 2 . Evaporation of metal contact pads on both ends of single SnO 2 -nanowires enable their direct use as sensing elements. The devices are very sensitive and are able to detect concentrations of CO and CH 4 as low as a few ppm.I.