Crystalline titanium dioxide (TiO2) powders have been prepared by the modified alkoxide method at low temperatures. The modified synthesis includes two steps: the precipitation of amorphous powder and the transformation of the amorphous structure to crystalline anatase or rutile. The temperature of both reactions was 50 degrees C, and all experiments were made under normal pressure. It was found that the amorphous powder breaks down into extremely acidic solution and that the final crystalline structure after the acid treatment depends on the acidity of the solution. Lower acidity promotes anatase structure, while in case of higher amount of acid the final crystal form is rutile. (C) 2007 Elsevier B.V. All rights reserved.