Magnesium hydride-graphite composites produced via ball milling exhibit fast H 2 desorption/absorption kinetics; moreover, their activation behaviour is particularly attractive if compared with MgH 2 -based materials obtained so far. In this work, we report the phase analysis (by X-ray diffraction) and investigate the crystal structure and the desorption behaviour (using a home-made Sievert apparatus) of MgH 2 -graphite composites produced by ball milling. Milling with graphite is found to improve the desorption rate of MgH 2 changing the reaction mechanism.