Reaction sintered dense zirconia-mullite composites were prepared by isostatically pressing from zircon flour and reactive alumina with different proportions of TiO2 and Cr2O3 additives. The pressed compacts were sintered at different elevated temperatures with variable soaking times. Microstructures and phase development in the sintered compacts were analysed to assess the influence of the additives on the properties of the zirconia mullite composite.