  We consider how, for quasi-degenerate neutrinos with tri-bi-maximal mixing at
a high-energy scale, the mixing angles are affected by radiative running from
high to low-energy scales in a supersymmetric theory. The limits on the
high-energy scale that follow from consistency with the observed mixing are
determined. We construct a model in which a non-Abelian discrete family
symmetry leads both to a quasi-degenerate neutrino mass spectrum and to near
tri-bi-maximal mixing.
