Among samples of Mg-Ni, Mg-Ni-5Fe(2)O(3),and Mg-Ni-5Fe, Mg-Ni-5Fe had the highest hydriding and dehydriding rates. For the as-milled Mg-Ni-5Fe alloy and the hydrided Mg-Ni-5Fe alloy after activation, the weight percentages of the constituent phases were calculated using the FullProf program. The creation of defects and the diminution of Mg particle size through reactive mechanical grinding and hydriding dehydriding cycling, and the formation of the Mg2Ni phase are considered to increase the hydriding and dehydriding rates. Mg-14Ni-2Fe-2Ti-2Mo had higher hydriding and dehydriding rates than did any of the other samples (Mg-Ni, Mg-Ni-5Fe(2)O(3), Mg-Ni-5Fe, and Mg-14Ni-6Fe(2)O(3)) prepared in this work. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.