316LVM, an austenitic stainless steel, was implanted at 49 keV with molybdenum ions. Implantation doses varied between 1x10 1 5 and 3.5x10 1 6 ions cm - 2 . The structure of the implanted layer was examined by grazing incidence X-ray diffraction. As a function of ion dose, expanded fcc austenite was first observed, then a tetragonal distortion of the fcc lattice occurred. Above 8x10 1 5 ions cm - 2 a new bcc structure appeared and finally the implanted layer was amorphized.