The Mesoporous TiO2 hollow spheres are synthesized by a solvothermal reaction without any surfactant and template. The reaction conditions such as reaction temperature, type of precursor, solvent used and their influence on the synthesis of TiO2 hollow spheres are investigated. The synthesized TiO2 hollow spheres are characterized by X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), focused ion beam (FIB) SEM, Barrett-Emmett-Teller (BET) surface areas, and UV-visible diffused reflectance spectroscopy. The synthesized TiO2 spheres have obtained different diameters ranging from 700 nm to 1.79 mu m at different reaction temperatures. The shell is composed of numerous single crystalline nanoparticles. The morphology and interiors of the spheres strongly depend upon the experimental parameters such as reaction temperature and a kind of solvent. Especially, interiors of TiO2 hollow spheres such as mesoporous, double shell and single wall structures at various reaction temperatures are discussed with the aid of TEM and FIB SEM measurements. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.058201jes].