Hydrotalcites, which are anionic clays, have been synthesized by the sol-gel technique from magnesium ethoxide, aluminum tri-sec-butoxide, and aluminum acetylacetonate. Initially a colloidal solution is obtained which gels and is thermally stabilized. The local and average structure are studied comparing the electron microscopy results with the XRD patterns. One of the main features of these materials is the high specific area (around 150 m(2)/g), if compared with the natural hydrotalcites areas.