The objective of this work was to compare the hydriding kinetics of Mg2Ni with that of Mg1.9Al0.1Ni and study the influence of the initial hydrogen pressure on the hydriding kinetics in the two-phase (alpha-beta) region of the Mg2-xAlxNi (x = 0, 0.1) alloys. Experiments were carefully performed under the initial hydrogen pressure ranging from 0.275 to 1.203 MPa and isothermal condition. The obtained hydrogen absorption kinetic curves were fitted using various rate equations to reveal the mechanism of the hydriding process. It was found that the three-dimensional diffusion process dominated the hydrogen absorption. The experimental investigation suggested that increase of the initial hydrogen pressure resulted in an acceleration of hydriding transformed fraction and the kinetic characteristics of Mg2Ni alloy was improved by substituting Al for Mg due to difference in hydride structure, particle size. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.