  We consider the problem of neutrino masses and mixing within the general
framework of standard (type-I) seesaw models leading to three light neutrinos.
Under the assumption of a hierarchical neutrino mass spectrum \lambda^4:
\lambda : 1, consistent with present data, we examine possible lopsided
patterns for the neutrino Yukawa couplings that can account for the observed
mixing angles, including a small but non-vanishing |U_{e3}|. An embedding of
the above within a general class of SO(10) models is also considered.
