One-dimensional (1D) nanostructures of semiconductor oxides are of interest for various applications including gas sensors. For gas sensors, nanostructures have advantages of improved gas-sensing characteristics and have potential in fabrication of miniature sensor. In this paper, we review some of the work done in our laboratory towards growth of nanostructures of SnO2, ZnO and CuO and hierarchical nano-heterostructures of CuO:W18O49, SnO2: W18O49 and ZnO:18O49 as well as investigation of their gas-sensing properties. All nanostructures except CuO have been prepared by thermal evaporation technique. CuO nanowires have been grown by thermal oxidation of copper foils under oxygen atmosphere. Gas sensing has been investigated in: isolated 1D structures placed between two electrodes; films prepared from their suspension in organic solvents or direct growth of nanostructured films on substrates. The results show that isolated 1D nanostructures of pure SnO2 and ZnO are highly sensitive for room temperature detection of H2S and NO gases respectively while SnO2:W18O49 heterostructures may be used for the detection of chlorine.