  The motivation and the current status of top-down models as sources of
ultrahigh energy cosmic rays (UHECR) are reviewed. Stimulated by the AGASA
excess, they were proposed as the main source of UHECRs beyond the GZK cutoff.
Meanwhile searches for their signatures have limited their contribution to the
UHECR flux to be subdominant, while the theoretical motivation for these
searches remained strong: Topological defects are a generic consequence of
Grand Unified Theories and superheavy particles are a creditable dark matter
candidate. While Fermi/GLAST results should help to improve soon bounds on
topological defects from the diffuse gamma-ray background, the most promising
detection method are UHE neutrino searches. Superheavy dark matter can be
restricted or detected by its characteristic galactic anisotropy combined with
searches for UHE photons.
