  We determine the nu_{R} Majorana mass matrix from the experimental data on
neutrino oscillations in the framework of a see-saw SO(10) model, where we
impose the condition (M^R)_{33} = 0 to avoid too large fine-tunings in the
see-saw formula. We find a class of solutions with the two lowest neutrino
masses almost degenerate and the scale of the matrix elements of M^R in the
range 10^{11} -10^{12} GeV in agreement with Pati-Salam intermediate symmetry.
We find also solutions with smaller neutrino masses, for which the scale of M_R
depends on the solution to the "solar neutrino problem" and on the value of the
component of \nu_e along the highest mass eigenstate, U_{e3}.
