The nanocrystalline Mg + x wt% LaMg2Ni (x = 0, 5, 10, 20, 30) composites were prepared by reactive ball-milling, their microstructure and hydrogen storage characteristics were investigated. The results show that the addition of LaMg2Ni improves the hydriding rate and capacity. The hydriding capacity of the Mg + x wt% LaMg2Ni (x = 5, 10, 20, 30) composites are all above 4.1 wt% at 120 degrees C and above 4.3 wt% at 180 degrees C within 6000 s. Moreover, the addition of LaMg2Ni also improves the dehydriding performance of the composites. The main reason for the improvement of hydriding/dehydriding properties investigated by XRD and SEM shows that the synergistic effect among the multiphase nanocrystalline Mg-based structures make hydrogen easily absorbed/desorbed on the interface of the matrix. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.