Two kinds of monophasic gels were synthesized from silicon ethyl ester (TEOS) and aluminium nitrate mixture by varying the water-alcohol content of the system. The mullitization reaction paths of the two gels were studied by differential thermal analysis (DTA) and X-ray diffraction techniques. The first kind of monophasic gel exhibited cubic mullite (Si-AI spinel) on the 980 ~ exotherm and a further two more broad exotherms at 11 50 and 1 243 ~ This phenomenon resembles the DTA thermogram of a kaolinitic clay. The later two exotherms have been explained as due to the formation of mutlite by two different reaction paths from the two phases appearing in the 980~ exotherm. Nucleation and crystallization of mullite from amorphous alumino silicate phase takes place at --~ 11 50 ~ and transformation of cubic mullite to orthorhombic mullite takes place at ,-~ 1 245 ~ The second kind of monophasic gel exhibited only one exotherm and produced exclusively tetragonal mullite at 980 ~ The results suggest that pure mullite formation is possible when water induced hydrolysis of TEOS is avoided during the gelation process.