  We derive the renormalization group equations (RGE) for the flavour coupling
matrices of the effective dimension-five operators which yield Majorana
neutrino masses in the multi-Higgs-doublet Standard Model; in particular, we
consider the case where two different scalar doublets occur in those operators.
We also write down the RGE for the scalar-potential quartic couplings and for
the Yukawa couplings of that model, in the absence of quarks. As an application
of the RGE, we consider two models which, based on a mu-tau interchange
symmetry, predict maximal atmospheric neutrino mixing, together with U_{e3} =
0, at the seesaw scale. We estimate the change of those predictions due to the
evolution of the coupling matrices of the effective mass operators from the
seesaw scale down to the electroweak scale. We derive an upper bound on that
change, thereby finding that the radiative corrections to those predictions are
in general negligible.
