Hydrogenation properties and mechanical stability of pellets made starting from compressed ball-milled MgH(2) powders mixed with catalysts (Nb(2)O(5) and graphite) and a binding agent (aluminium powder) have been investigated. Structural characterization with X-ray diffraction and gas-solid reaction kinetic and thermodynamic tests with a Sievert's apparatus have been done on the samples up to 50 hydrogen absorption/desorption (aid) cycles. The best cycling behaviour and mechanical strength stability have been observed for pellets of catalysed MgH(2) powders added with 5 wt% aluminium annealed in vacuum at 450 degrees C before starting the aid cycles. This mechanical stability to cycles has been attributed to the formation of a solid solution of aluminium in magnesium. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.