MgH(2) is a perspective hydrogen storage material whose main advantage is a relatively high hydrogen storage capacity (theoretically, 7.6 wt.% H(2)). This compound, however, shows poor hydrogen desorption kinetics. Much effort was devoted in the past to finding possible ways of enhancing hydrogen desorption rate from MgH(2), which would bring this material closer to technical applications. One possible way is catalysis of hydrogen desorption. This paper investigates separate catalytic effects of Ni, Mg(2)Ni and Mg(2)NiH(4) on the hydrogen desorption characteristics of MgH(2). It was observed that the catalytic efficiency of Mg(2)NiH(4) was considerably higher than that of pure Ni and non-hydrated intermetallic Mg(2)Ni. The Mg(2)NiH(4) phase has two low-temperature modifications below 508 K: un-twinned phase LT1 and micro-twinned phase LT2. LT1 was observed to have significantly higher catalytic efficiency than LT2. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.