Complete CaTiO3 formation has been found to occur in CaCO3-TiO2 (anatase or rutile) mixtures subjected to mechanical activation by high energy milling. Such formation has been demonstrated to occur by rapid heating (20 K/min) up to 1250degreesC. The first stage of the reaction takes place as CaO forms, the reaction, then, proceeds at higher temperatures reaching its maximum rate at about 1000degreesC. Alternatively CaTiO3 formation can be effected by 12-h annealing of the activated mixtures at temperatures between 750 and 850degreesC. Partial CaTiO3 formation was realized when starting from physical mixtures neither by rapid heating to 1250degreesC nor by 12-h annealing at temperatures as high as 1000degreesC. (C) 2004 Kluwer Academic Publishers.