  The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by the
Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma-Ray
Observatory provides a unique opportunity to examine in detail the diffuse
gamma-ray emission. The observed diffuse emission has a Galactic component
arising from cosmic-ray interactions with the local interstellar gas and
radiation as well an almost uniformly distributed component that is generally
believed to originate outside the Galaxy. The results of the observations have
been interpreted as the extragalactic high-energy gamma-ray emission arising
primarily from unresolved gamma-ray-emitting blazars.
  We considered another possible origin of the diffuse gamma-ray flux, namely,
as originating from the annihilation of the antiprotons with the interstellar
medium.
