Mg-23.5 wt% Ni and Mg-23.5 wt% Ni-5 wt% Cu alloys for hydrogen storage were prepared by melt spinning and crystallization heat treatment. The alloys were ground by a planetary ball mill for 2 h in order to obtain a fine powder. The activated Mg-23.5Ni and Mg-23.5Ni-5Cu alloys absorbed 4.34 and 4.84 wt% H, respectively, at 573 K under 12 bar H-2 for 60 min. The activated Mg-23.5Ni and Mg-23.5Ni-5Cu alloys desorbed 4.27 and 4.81 wt% H, respectively, at 573 K under 1.0 bar H-2 for 30 min. The hydriding rates of the alloys are quite high, even at 473 K, while the dehydriding rates of the samples at 473 K are nearly zero. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.