  We propose a new scenario in a class of superstring derived standard--like
models that explains the suppression of the left--handed neutrino masses. Due
to nonrenormalizable terms and the breaking of the $U(1)_{Z^\prime}$ symmetry a
generalized see--saw mechanism takes place. Contrary to the traditional
see--saw mechanism in GUTs, the see--saw scale and the right--handed neutrino
mass scale are suppressed relative to the $U(1)_{Z^\prime}$ breaking scale.
