This paper presents a two dimensional mathematical model to evaluate transient heat and mass transfer in the metal hydride bed. Thermophysical properties of metal hydrides in this model depend on the reacted fraction. Hydriding and dehydriding kinetics are described by new model presented by Inomata et al. [1]. The result on velocity, temperature and composition distribution are presented and discussed. Moreover this paper discusses in detail the validity of several assumptions that the local gas temperature is equal to bed temperature and that the convection term in an energy equation for gas phase is neglected. (C) 2000 International Association for Hydrogen Energy.