The kinetics of the sorption of molecular hydrogen by ZrCo and Zi0.8Ti0.3Mn1.9 was investigated as function of temperature at several constant pressures of hydrogen. A comparison between the isothermal hydrogen sorption rates by ZrCo, Zr0.8Ti0.3Mn1.9 and LaNi4.7A10.3 is given and reaction mechanisms are discussed. From fittings of the experimental results to well known gas/solid reaction rate laws it was concluded that the reaction mechanisms of the reaction with ZrCo is complex and dependant upon the prevailing reaction conditions. The hydrogen sorption rate by the powder of all three IMC's was found to be second order in hydrogen pressure.