The alloy, Mg2Ni, is a good candidate for the storage of hydrogen. One problem associated with the use of this alloy for hydrogen storage is the difficulty of its activation for initial hydrogen uptake. A great deal of research has been done in this area. However, the resulting methods require hazardous conditions and reagents and/or prohibitively long periods of time. It has been found in this laboratory that water vapor can be used to activate Mg2Ni for hydrogen uptake in as little as 1 h at ambient temperature and pressure. This finding is particularly interesting considering the long-held view of water acting as a poison in metallic hydrogen storage systems.