Room temperature grinding by a planetary ball mill has been applied to four kinds of mixtures prepared from CaO or Ca(OH)(2) and anatase or rutile (TiO2). Crystalline CaTiO3 can be mechanochemically synthesized by grinding the mixture of CaO with both forms of TiO2 but is difficult to obtain from the mixtures of Ca(OH)(2) and TiO2. These observations are in contrast to the results of Avvakumov et al. [E.G. Avvakumov, E.T. Devyatkina, N.V. Kosova, Mechanochemical reactions of hydrated oxides, J. Solid State Chem. 113 (1994) 379-383] and are in agreement with the thermodynamic data. The reactivity of CaO or Ca(OH)(2) with anatase is slightly higher than is the case with rutile. Heating of the ground mixtures at about 900-1200 K is found to be effective for producing crystalline CaTiO3.