Ion-beam-induced migration of an implanted impurity is studied using a phenomenological model involving diffusion of the impurity, vacancies and coupling between their motion. Redistribution of implanted Mn, Fe and Ni in Al is experimentally observed using the RES technique and analyzed using the phenomenological model. Implantations are carried out at 200 keV, to a dose of 1 10 1 6 ions cm - 2 and at temperatures ranging from 77 K to 373 K. Coupled continuity equations for implanted atom and vacancy fluxes are solved to obtain theoretical fits to the experimental concentration vs. depth profiles. An effective diffusion coefficient describing radiation-induced thermal and athermal processes is obtained from the theoretical fits and is found to have a value a few orders of magnitude higher than the normal diffusion coefficients.