  Maximum mixing in atmospheric neutrino oscillation, as well as vanishing of
the MNS matrix element $U_{e3}$, are consequences of a 2-3 symmetry, under
which the neutrino mass matrix is invariant under the interchange of second and
third generation neutrinos. These predictions of the 2-3 symmetry are
consistent with the results of Super-Kamiokande, K2K, and CHOOZ experiments. If
the symmetry is exact at a high-energy scale set by right-handed neutrinos, a
deviation from these predictions generated by renormalization-group corrections
will occur at experimental energies. With an MSSM dynamics, the result can be
made to agree with a global fit of the neutrino data, if normal hierarchy is
assumed on the neutrino mass spectrum and if the mass of the electron-neutrino
is at least about 0.025 eV. The presence of this mass lower bound is a novel
and interesting feature of the symmetry that can be falsified by future
experiments. Of the three viable solar neutrino solutions, only LMA gives a
sizable MNS matrix element $U_{e3}$ that can hopefully be detected in future
reactor experiments. Inverted neutrino mass hierarchy is not permitted by this
symmetry.
