  The large mixing angle (LMA) MSW solution to the solar neutrino problem seems
favored by the data at the moment over the small mixing angle (SMA) MSW
solution and the vacuum (VAC) solution. In this paper the various main types of
models of neutrino masses and mixings are studied from the point of view of how
naturally they can give the LMA solution. Special attention is given to a very
simple type of "lopsided" SU(5) model.
