Barium titanate (BaTiO3) thin films prepared on magnesia, silicon and strontium titanate substrates by r.f. sputtering has been investigated. As a function of substrate and annealing temperatures, the crystal structure and shape were examined by X-ray diffraction and scanning electron microscopy. Thin films were grown on both MgO and silicon substrates; they were amorphous when deposited on MgO if the substrate temperature was less than 450 degrees C, while for those grown on silicon the temperature had to be less than 500 degrees C. Above these elevated temperatures, the films were crystalline, with cubic symmetry. After annealing the thin firms on magnesia, the crystal structure changed from cubic to tetragonal phase above 1100 degrees C; the annealing thus caused the grain growth of the BaTiO3. The thin films on SrTiO3 were found to be c-axis oriented tetragonal films for a substrate temperature above 500 degrees C.