Though the alloy, Mg,Ni, has desirable properties for storage of hydrogen, its application has been hindered by the difficulty of its initial activation for hydrogen uptake. A number of methods have been reported for activation of Mg,Ni. While some of these methods utilize aqueous solutions, there has been no report of activation with pure water. It has been demonstrated in this laboratory that magnesium nickel alloy can be activated for hydrogen uptake by treatment with water for as little as 2 min. Increasing the treatment time with water increases the amount of hydrogen absorbed and increases the longevity of the activation. Thermal data, scanning electron microscopic data, and x-ray photoelectron spectroscopic data are presented in a discussion of the activation of magnesium nickel alloy with water,