  Phenomenological bounds on the neutrino mixing matrix U are used to determine
numerically the allowed range of real elements (CP conserving case) for the
symmetric neutrino mass matrix Mn (Majorana case). For this purpose an adaptive
Monte Carlo generator has been used. Histograms are constructed to show which
forms of the neutrino mass matrix Mn are possible and preferred. We confirm
results found in the literature which are based on analytical calculations,
though a few differences appear. These cases correspond to some textures with
two zeros. The results show that actually both normal and inverted mass
hierarchies are still possible at 3 sigma confidence level.

High Energy Physics - Phenomenology