Medium energy ion scattering has been used to investigate the possible interdiffusion of Co and V at the Co/V interface in the Co/V/MgO(1 0 0) system at room temperature and after annealing in the temperature range from 100 to 500 °C. The Co and V composition and structure as a function of depth has been studied using two-dimensional maps of the scattered ion energy versus scattering angle and with the corresponding projections onto the angle axis over a small energy range (angle spectrum) and onto the energy axis over a small scattering angle range (energy spectrum). At room temperature only limited interdiffusion at the Co/V interface can be inferred from the analysis of the experimental data, while at 300 °C and higher drastic changes are observed at the Co/V interface in terms of sharpness and composition. Furthermore, a structural change is observed after annealing at 500 °C as a consequence of the V and/or Co interdiffusion.