The various Mg-B-Al-H systems composed of Mg(BH4)(2) and different Al-sources (metallic Al, LiAlH4 and its decomposition products) have been investigated as potential hydrogen storage materials. The role of Al was studied on the dehydrogenation and the rehydrogenation of the systems. The results indicate that the different Al-sources exhibit a similar improving effect on the dehydrogenation properties of Mg(BH4)(2). Taking the Mg(BH4)(2) + LiAlH4 system as an example, at first LiAlH4 rapidly decomposes into LiH and Al, then Mg(BH4)(2) decomposes into MgH2 and B, finally the MgH2 reacts with Al, LiH and B, which forms Mg3Al2 and MgAlB4. The system starts to desorb H-2 at 140 degrees C and desorbs 3.6 wt.% H-2 below 300 degrees C, while individual Mg(BH4)(2) starts to desorb H-2 at 250 degrees C and desorbs only 1.3 wt.% H-2 below 300 degrees C. The isothermal desorption kinetics of the Mg-B-Al-H systems is about 40% faster than that of Mg(BH4)(2) at the hydrogen desorption ratio of 90%. In addition, the Mg-B-Al-H systems show partial reversibility at moderate temperature and pressure. For Al-added system, the product of rehydrogenation is MgH2, while for LiAlH4-added system the product is composed of LiBH4 and MgH2. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.