If neutrino masses and mixings are suitable to explain the atmospheric and solar neutrino fluxes, this amounts to contributions to FCNC processes, in particular μ → e, γ. If the theory is supersymmetric and the origin of the masses is a see-saw mechanism, we show that the prediction for BR(μ → e, γ) is in general larger than the experimental upper bound, especially if the solar data are explain...