  We present solutions for the structure of the boundary layer where the
accretion disk meets the neutron star, which is expected to be the dominant
source of high-energy radiation in low-mass X-ray binaries which contain weakly
magnetized accreting neutron stars.
  We find that the main portion of the boundary layer gas is hot (> ~10^8 K),
low in density, radially and vertically extended, and optically thick to
scattering but optically thin to absorption. It will produce large X-ray
luminosity by Comptonization. Energy is transported inward by viscosity,
concentrating the energy dissipation in the dense, optically thick zone close
to the stellar surface. We explore the dependence of the boundary layer
structure on the mass accretion rate, the rotation rate of the star, the alpha
viscosity parameter and the viscosity prescription.
  Radiation pressure is the dominant source of pressure in the boundary layer;
the flux is close to the Eddington limiting flux even for luminosities well
below (~0.01 times) L(Edd). At luminosities near L(Edd), the boundary layer
expands radially, and has a radial extent larger than one stellar radius.
  Based on the temperatures and optical depths which characterize the boundary
layer, we expect that Comptonization will produce a power-law spectrum at low
source luminosities. At high luminosities, a Planckian spectrum will be
produced in the dense region where most of the energy is released, and modified
by Comptonization as the radiation propagates outward.
