SiO2 nanotubes with tunable diameters and lengths have been successfully synthesized via a simple in situ templatelike process by thermal evaporation of SiO, ZnS, and GaN in a vertical induction furnace. The structure and morphologies were systematically investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectrometry. Studies found that both the diameters and lengths of the SiO2 nanotubes can be effectively tuned by simply changing the reaction temperatures. The range of changes was from 30 nm (diameter) and several hundred micrometers (length) at 1450 C to 100 nm (diameter) and 2-10 micrometers (length) at 1300 C. Varying some other experimental parameters results in the formation of additional SiO2-based nanostructures, such as core-shell ZnS-SiO2 nanocables, ZnS nanoparticle filled SiO2 nanotubes, and fluffy SiO2 spheres. Based on the observations, an in situ templatelike process was proposed to explain the possible growth mechanism.