  A search for diffuse neutrinos with energies in excess of 10^5 GeV is
conducted with AMANDA-II data recorded between 2000 and 2002. Above 10^7 GeV,
the Earth is essentially opaque to neutrinos. This fact, combined with the
limited overburden of the AMANDA-II detector (roughly 1.5 km), concentrates
these ultra high-energy neutrinos at the horizon. The primary background for
this analysis is bundles of downgoing, high-energy muons from the interaction
of cosmic rays in the atmosphere. No statistically significant excess above the
expected background is seen in the data, and an upper limit is set on the
diffuse all-flavor neutrino flux of E^{-2} $\Phi$_{90%CL} < 2.7 $\times$
10^{-7} GeV cm^{-2} s^{-1} sr^{-1} valid over the energy range of 2 $\times$
10^5 GeV to 10^9 GeV. A number of models which predict neutrino fluxes from
active galactic nuclei are excluded at the 90% confidence level.
