Continuous phase transition from cubic-to-tetragonal depended on reaction conditions was found in the hydrothermally synthesized BaTiO3. The BaTiO3 particles were characterized by powder X-ray diffraction (XRD), transmission electron microscope (TEM), high resolution TEM (HR-TEM), Raman spectra and thermal gravimetric analysis (TGA) techniques. A competitive process between the kinetic control and the thermodynamic control resulted in the crystal structure transition. In these structure-transitional products, the "cubic-rich" BaTiO3 exhibited a stronger Ba2+ ions leaching ability in aqueous medium compared with the "tetragonal-rich" BaTiO3 because the two types of samples had differences in crystal structures and the amount of lattice defects contained. (C) 2008 Elsevier B.V. All rights reserved.