In this paper, we review our recent results on hydrogen storage properties in light metals(M)-nitrogen(N)-hydrogen(H) systems prepared by mechanochemical method. At first, the composite mixture of LiH and LiNH2 doped with TiCl3 as a catalyst was prepared by ball milling for 2 h under a H-2 gas pressure of 1 MPa. The TDS profile indicated that similar to 6 mass% H-2 was desorbed by the reaction LiH + LiNH2 <-> Li2NH + H-2 in the temperature range from 150 to 250 degrees C under a He gas flow at a heating rate of 5 degrees C min(-1), but the H-desorption equilibrium pressure P-H2 was similar to 0.1 MPa at 250 degrees C. This temperature is too high for onboard use, indicating that further improvement is necessary to destabilize the above Hstorage reaction. For that, we clarified the H-desorption mechanism by the isotopic exchange experiments, on the basis of which we designed a new Li-Mg-N-H composite system with the reaction 8LiH + 3Mg(NH2)(2)<-> 4Li(2)NH + Mg3N2 + 8H(2). This composite materials desorbed similar to 7 mass% H-2 in the range from 120 to 200 degrees C and the H-desorption equilibrium pressure P-H2 was higher than 5 MPa at 200 degrees C, indicating that this system has an excellent potential for onboard applications. (c) 2006 Elsevier B.V. All rights reserved.