  If neutrino masses and mixings are suitable to explain the atmospheric and
solar neutrino fluxes, this amounts to contributions to FCNC processes, in
particular $\mu\to e, \gamma$. If the theory is supersymmetric and the origin
of the masses is a see-saw mechanism, we show that the prediction for
BR($\mu\to e, \gamma$) is in general larger than the experimental upper bound,
especially if the solar data are explained by a large angle MSW effect, which
recent analyses suggest as the preferred scenario.
