We have investigated the hydrogen storage properties of a ball-milled mixture of 3Mg(NH2)(2) and 8LiH after first synthesizing Mg(NH2)(2) by ball milling MgH2 under an atmosphere of NH3 gas at room temperature. The thermal desorption mass spectra of the mixture without any catalysts indicated that a large amount of hydrogen (similar to7 wt %) was desorbed from 140 degreesC, and the desorption peaked at similar to190 degreesC under a heating rate of 5 degreesC/min with almost no ammonia emission. Moreover, the reversibility of the hydrogen absorption/desorption reactions was confirmed to be complete. The above results indicate that this system is one of the promising metal-N-H systems for hydrogen storage.