  We give an overview over models in which cosmic rays above 1 EeV = 10**(18)
eV are produced by the decay of supermassive "X" particles released from
topological defects possibly created in cosmological phase transitions. We note
that, for an interesting particle physics parameter range, these models are
still consistent with current data, and discuss signatures for the topological
defect mechanism which can be tested by the next generation experiments.
