Storage and transportation of hydrogen in solid state using metal hydride reactors has been recognized as one of the most convenient and safe techniques. A large variety of materials have been suggested for this purpose. However, drawbacks such as large weight and poor cycling behavior have hampered the practical application of such storage devices. Metal hydride reactors are complicated heat and mass exchangers and need to be designed optimally from the thermal performance point of view. Heat and mass transfer problems in such devices being investigated both analytically and experimentally at the author’s laboratory are reviewed here. It is felt that in addition to the thermo-physical properties and configuration of the hydride bed, diffusion of hydrogen gas in the void space and also within the alloy particle is very important.