In this work, we report the synthesis, characterization and destabilization of lithium aluminum hydride by ad-mixing nanocrystalline magnesium hydride (e.g. LiAlH4 + nanoMgH(2)). A new nanoparticulate complex hydride mixture (Li-nMg-Al-H) was obtained by solid-state mechano-chemical milling of the parent compounds at ambient temperature. Nanosized MgH2 is shown to have greater and improved hydrogen performance in terms of storage capacity, kinetics, and initial temperature of decomposition, over the commercial MgH2. The pressure-composition isotherms (PCI) reveal that the destabilized LiAlH4 + nanoMgH(2) possess similar to 5.0 wt.% H-2 reversible capacity at T <= 350 degrees C. Van't Hoff calculations demonstrate that the destabilized (LiAlH4 + nanoMgH(2)) complex materials have comparable enthalpy of hydrogen release (similar to 85 kJ/mole H-2) to their pristine counterparts, LiAlH4 and MgH2. However, these new destabilized complex hydrides exhibit reversible hydrogen sorption behavior with fast kinetics. (c) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.