  We review the current status of general relativistic studies for coalescences
of black hole--neutron star binaries. First, high-precision computations of
black hole--neutron star binaries in quasiequilibrium circular orbits are
summarized, focusing on the quasiequilibrium sequences and the mass-shedding
limit. Next, the current status of numerical-relativity simulations for the
merger of black hole--neutron star binaries is described. We summarize our
understanding for the merger process, tidal disruption and its criterion,
properties of the merger remnant and ejected material, gravitational waveforms,
and gravitational-wave spectra. We also discuss expected electromagnetic
counterparts to black hole--neutron star coalescences.
