The large-scale flowerlike ZnO nanostructures, consisting of many aggregative nanorods with the diameter of about 60 nm, were prepared by a simple and facile hydrothermal route. The toluene sensing properties of the pure ZnO and TiO₂-doped ZnO nanostructures were tested at different operating temperatures from 160 to 390 °C and toluene concentrations ranging from 1 to 3000 ppm. The results indicate that the response of the ZnO nanostructures towards toluene was enhanced significantly by TiO₂ doping, which was deposited onto the ZnO products by evaporation. It is found that the TiO₂-doped ZnO sensor exhibits remarkably enhanced response of 17.1 at the optimal operating temperature of 290 °C to 100 ppm toluene, which has been improved up from 7.4 at 390 °C from pure ZnO nanostructures.