SiO2, TiO2 and AlO(OH) powders obtained by the sol-gel method were investigated by transmission electron microscopy. The massradius relation was used to determine the fractal dimensions from the images. These fractal dimensions were corrected in order to obtain the powder fractal dimensions. The results indicate a good fractal behavior and high fractal dimensions. (C) 2004 Elsevier B.V All rights reserved.