  We formulate and discuss a 4-dimensional SUSY version of an A4 model for
tri-bimaximal neutrino mixing which is completely natural. We also study the
next-to-the-leading corrections and show that they are small, once the ratios
of A4 breaking VEVs to the cutoff are fixed in a specified interval. We also
point out an interesting way of presenting the A4 group starting from the
modular group. In this approach, which could be interesting in itself as an
indication on a possible origin of A4, the lagrangian basis where the symmetry
is formulated coincides with the basis where the charged leptons are diagonal.
If the same classification structure in A4 is extended from leptons to quarks,
the CKM matrix coincides with the unit matrix in leading order and a study of
non leading corrections shows that the departures from unity of the CKM matrix
are far too small to accomodate the observed mixing angles.
