Magnesium hydride with 7 wt.% of various metal halide additives (ZrF4, TaF5, NbF5 and TiCl3) were ball milled, and the influence of these dopants on the kinetics of absorption and desorption was studied. The pressure composition temperature isotherms (P C T) measured by Sieverts' apparatus did not show thermodynamic changes in the studied materials. Moreover, XPS studies demonstrated that the metal halides used in this study (except ZrF4) took part in the partial and full disproportionation reactions directly after milling and the first desorption/absorption cycle. The catalytic effect of metal halides on the Mg hydrogenation/dehydrogenation process was caused by the formation of pure transition metal and/or the MgF2 phase, which led to the influence of two simultaneous factors on the sorption properties of the MgH2. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.