Hydrogenation / dehydrogenation properties of a series of ternary face centered cubic (FCC) hydrides “Mg7MHx” (M = Sc, Ti, V, Zr, Nb, Hf and Ta), which were prepared by a high-pressure technique, were investigated. Differential scanning calorimeter (DSC) measurements under hydrogen atmosphere revealed that these hydrides exhibited reversible hydrogen releasing and re-storing properties at around 600 and 560 K, respectively. These releasing temperatures are lower by 100 ~ 120 K than that of MgH2. Furthermore, pressure-composition isotherm at 523 K shows that these FCC hydrides release 3.8 - 5 wt. % hydrogens.