Grazing X-ray diffraction was used to study in details the behaviour of two spinels, ZnAl 2 O 4 and MgAl 2 O 4 irradiated by swift ions. Such an irradiation allows to have an important irradiated depth and then accurate diffraction diagrams. Rietveld refinement done on these diagrams clearly show an order-disorder transition due to a melting of cations under irradiation in these two spinels. More especially, these results clearly exhibit that no new phase is created under irradiation in MgAl 2 O 4 . Raman spectroscopy, sensitive to the crystallographic space group, seems to confirm this analysis.