  I give a brief review of high energy gamma-ray signatures of dark matter. The
decay of massive $X$-particles and subsequent hadronization have been suggested
as the origin of the highest energy cosmic rays. Propagation over cosmological
distances to Earth (as would be the case in some topological defect origin
models for the $X$-particles) results in potentially observable gamma-ray
fluxes at GeV energies. Massive relic particles on the other hand, would
cluster in galaxy halos, including that of our Galaxy, and may give rise to
anisotropic gamma ray and cosmic ray signals at ultra high energies. Future
observations above 100 Gev of gamma rays due to WIMP annihilation in the halo
of the Galaxy may be used to place constraints on supersymmetry parameter
space.
