In the present investigation alumina-mullite composites with various mole ratios of Al2O3 and SiO2 were generated by interacting fly ash with bauxite. The magnitude of sintering was examined by examining the characteristic properties of the sintered product which were subsequently correlated with generated crystalline phases and microstructure. The multiplicity of possible phase relations in this particular system is complex and the associated impurities played a vital role leading to liquid phase sintering. © 2008 Taylor and Francis Group, LLC.