  Three of the viable solutions of the solar neutrino problem are consistent
with close to maximal leptonic mixing:
$\sin^2\theta_{12}={1\over2}(1-\epsilon_{12})$ with $|\epsilon_{12}|\ll1$.
Flavor models can naturally explain close to maximal mixing if approximate
horizontal symmetries force a pseudo-Dirac structure on the neutrino mass
matrix. An experimental determination of $|\epsilon_{12}|$ and
sign($\epsilon_{12}$) can constrain the structure of the lepton mass matrices
and consequently provide stringent tests of such flavor models. If both
$|\epsilon_{12}|$ and $\Delta m^2_{21}$ are known, it may be possible to
estimate the mass scale of the pseudo-Dirac neutrinos. Radiative corrections to
close to maximal mixing are negligible. Subtleties related to the kinetic terms
in Froggatt-Nielsen models are clarified.
