  We compute the cosmological background radiation of gamma rays and neutrinos
due to neutralino annihilation in evolving dark matter halos, assuming the
observed dark matter is comprised of thermally excited neutralinos in the MSSM.
The spectrum of this gamma-ray background radiation does not show strong
annihilation line features, but could amount to a significant fraction of the
extragalactic gamma ray continuum flux observed by EGRET above a few GeV. The
corresponding cosmological neutrino background is weak compared to the
atmospheric foreground. Assuming full mixing, however, the cosmological
tau-neutrino background could be detectable with a flavor-discriminating
neutrino telescope in the energy range 10 GeV - 1 TeV. A small anisotropy of
the background radiation is expected, reflecting the local clustering of dark
matter halos along the supergalactic plane.
