Magnesium based hydrogen storage materials were prepared by a conventional melting and casting technique. Characterisation of microstructure and hydrogen sorption properties of the alloys was carried out. Additions of Al, Cu and Ni lead to the formation of eutectic mixtures, Mg-Mg17Al12, Mg-Mg2Cu and Mg-Mg2Ni, respectively, with an inter-lamellar spacing of a few hundred nanometers. 3d and 4d transition metals were also added to Mg based alloys and were found to form intermetallic compounds that were homogeneously dispersed in the alloys. The dehydrogenation rate of the Mg alloys was quantitatively analysed in order to determine the rate-limiting step for the hydrogen desorption kinetics. The catalysing role of each intermetallic compound for the hydrogen desorption kinetics is further discussed.