Effect of milling time on structure of pure Al powder and consequently on efficiency of Al-water reaction and hydrogen production is studied. Progress in milling process is studied considering changes in morphology, size, lattice imperfections and grains orientation of Al particles. Morphology of particles before and after the reaction is studied to establish a role of size and shape of particles on kinetics of the reaction. It is demonstrated that the formation of interlayer spaces within the investigated Al particles effectively increases hydrogen yield. Moreover, prolonged ball milling eliminates the interlayer spaces and decreases the rate of reaction of water with the powders. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.