The ability of decomposed Al2TiO5 to undergo reformation in phase composition has been characterised by neutron diffraction at elevated temperature and verified by differential thermal analysis. It is shown that the process of phase decomposition in metastable Al2TiO5 is reversible and that reformation occurs readily when decomposed Al2TiO5 is re-heated above 1300 degrees C. Subsequent decomposition of reformed Al2TiO5 during cooling below similar to 1200 degrees C is governed by the temperature-dependent atomic diffusion rates. Crown Copyright (c) 2008 Published by Elsevier B.V. All rights reserved.