  We have calculated the first dynamical evolutions of merging black
hole-neutron star binaries that treat the combined spacetime in a
nonperturbative general relativistic framework. Using the conformal flatness
approximation, we have studied how the location of the tidal disruption radius
with respect to the the black hole horizon and innermost stable circular orbit
(ISCO) affects the qualitative evolution of the system. Based on simple
arguments, we show that for a binary mass ratio q>~0.24, tidal disruption
occurs outside the ISCO, while the opposite is true for q<~0.24. When tidal
disruption occurs sufficiently far outside the ISCO, mass is transferred
unstably from the neutron star to the black hole, resulting in the complete
disruption of the neutron star. When tidal disruption occurs slightly within
the ISCO, we find that some of the mass forms an extremely hot disk around the
black hole. The resulting configurations in this case are excellent candidates
for the progenitors of short-hard gamma ray bursts.
